diff --git a/paperless-backend/eslint.config.mjs b/paperless-backend/eslint.config.mjs
index 4e9f827..adc3abf 100644
--- a/paperless-backend/eslint.config.mjs
+++ b/paperless-backend/eslint.config.mjs
@@ -28,8 +28,26 @@ export default tseslint.config(
     rules: {
       '@typescript-eslint/no-explicit-any': 'off',
       '@typescript-eslint/no-floating-promises': 'warn',
+      // any-getriebene Typsicherheits-Regeln: als Warnung statt Fehler, da die
+      // Paperless-NGX-API-Antworten (noch) untypisiert sind. Echte Bugs bleiben
+      // Fehler (alle nicht hier herabgestuften Regeln).
       '@typescript-eslint/no-unsafe-argument': 'warn',
-      "prettier/prettier": ["error", { endOfLine: "auto" }],
+      '@typescript-eslint/no-unsafe-member-access': 'warn',
+      '@typescript-eslint/no-unsafe-assignment': 'warn',
+      '@typescript-eslint/no-unsafe-call': 'warn',
+      '@typescript-eslint/no-unsafe-return': 'warn',
+      '@typescript-eslint/restrict-template-expressions': 'warn',
+      '@typescript-eslint/no-base-to-string': 'warn',
+      '@typescript-eslint/no-redundant-type-constituents': 'warn',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          argsIgnorePattern: '^_',
+          varsIgnorePattern: '^_',
+          caughtErrors: 'none',
+        },
+      ],
+      'prettier/prettier': ['error', { endOfLine: 'auto' }],
     },
   },
 );
diff --git a/paperless-backend/src/agrarmonitor/agrarmonitor-polling.service.ts b/paperless-backend/src/agrarmonitor/agrarmonitor-polling.service.ts
index 9e0cdab..0f1cd9e 100644
--- a/paperless-backend/src/agrarmonitor/agrarmonitor-polling.service.ts
+++ b/paperless-backend/src/agrarmonitor/agrarmonitor-polling.service.ts
@@ -59,7 +59,7 @@ export class AgrarmonitorPollingService implements OnModuleInit {
   }
 
   @Cron(process.env['AGRARMONITOR_POLLING_CRON'] || '0 */30 * * * *')
-  async scheduledPolling() {
+  scheduledPolling() {
     if (!process.env['AGRARMONITOR_POLLING_CRON']) return;
     this.runPolling().catch((err) =>
       this.logger.error('Cron-Polling-Fehler:', err),
@@ -67,7 +67,7 @@ export class AgrarmonitorPollingService implements OnModuleInit {
   }
 
   @Cron(process.env['AGRARMONITOR_UPLOAD_CHECK_CRON'] || '0 * * * * *')
-  async scheduledUploadCheck() {
+  scheduledUploadCheck() {
     if (!process.env['AGRARMONITOR_UPLOAD_CHECK_CRON']) return;
     this.processVerarbeiteteDocuments().catch((err) =>
       this.logger.error('Cron-Upload-Check-Fehler:', err),
diff --git a/paperless-backend/src/agrarmonitor/agrarmonitor.service.ts b/paperless-backend/src/agrarmonitor/agrarmonitor.service.ts
index 0d9cf76..0eb2c37 100644
--- a/paperless-backend/src/agrarmonitor/agrarmonitor.service.ts
+++ b/paperless-backend/src/agrarmonitor/agrarmonitor.service.ts
@@ -6,6 +6,7 @@ import {
   AesGcmCookieEncryptor,
   type AgrarmonitorConnectorResult,
 } from 'agrarmonitor-connector';
+import { getErrorMessage } from '../common/error.util';
 
 export interface AgrarmonitorStatusDto {
   connected: boolean;
@@ -95,13 +96,13 @@ export class AgrarmonitorService {
         registriert: registrierungStatus.registriert,
         freigeschaltet: freigeschaltetStatus.freigeschaltet,
       };
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.client = null;
       return {
         connected: false,
         registriert: null,
         freigeschaltet: null,
-        error: err?.message ?? 'Verbindung fehlgeschlagen',
+        error: getErrorMessage(err) || 'Verbindung fehlgeschlagen',
       };
     }
   }
diff --git a/paperless-backend/src/auth/authenticated-request.ts b/paperless-backend/src/auth/authenticated-request.ts
new file mode 100644
index 0000000..86531d4
--- /dev/null
+++ b/paperless-backend/src/auth/authenticated-request.ts
@@ -0,0 +1,24 @@
+import type { Request } from 'express';
+import type { Permission } from './permissions.enum';
+
+/** Vom JwtStrategy.validate() an `request.user` angehängte Identität. */
+export interface AuthenticatedUser {
+  userId: string;
+  email: string;
+  name: string;
+  preferredUsername: string | null;
+  groups: string[];
+  permissions: Permission[];
+}
+
+/** Vom ApiKeyGuard an `request.apiKeyMetadata` angehängte Schlüssel-Info. */
+export interface ApiKeyMetadata {
+  id: number;
+  name: string;
+}
+
+/** Express-Request mit der durch die Auth-Guards gesetzten Identität. */
+export interface AuthenticatedRequest extends Request {
+  user?: AuthenticatedUser;
+  apiKeyMetadata?: ApiKeyMetadata;
+}
diff --git a/paperless-backend/src/auth/jwt.strategy.ts b/paperless-backend/src/auth/jwt.strategy.ts
index 1153c05..325072f 100644
--- a/paperless-backend/src/auth/jwt.strategy.ts
+++ b/paperless-backend/src/auth/jwt.strategy.ts
@@ -4,6 +4,15 @@ import { Strategy, ExtractJwt } from 'passport-jwt';
 import { ConfigService } from '@nestjs/config';
 import { passportJwtSecret } from 'jwks-rsa';
 import { mapGroupsToPermissions } from './permissions.enum';
+import type { AuthenticatedUser } from './authenticated-request';
+
+interface JwtPayload {
+  sub: string;
+  email: string;
+  name?: string;
+  preferred_username?: string;
+  groups?: string[];
+}
 
 @Injectable()
 export class JwtStrategy extends PassportStrategy(Strategy, 'jwt') {
@@ -24,19 +33,12 @@ export class JwtStrategy extends PassportStrategy(Strategy, 'jwt') {
     });
   }
 
-  validate(payload: any): {
-    userId: string;
-    email: string;
-    name: string;
-    preferredUsername: string | null;
-    groups: string[];
-    permissions: any[];
-  } {
-    const groups = payload.groups || [];
+  validate(payload: JwtPayload): AuthenticatedUser {
+    const groups = payload.groups ?? [];
     return {
       userId: payload.sub,
       email: payload.email,
-      name: payload.name || payload.preferred_username,
+      name: payload.name || payload.preferred_username || '',
       preferredUsername: payload.preferred_username ?? null,
       groups: groups,
       permissions: mapGroupsToPermissions(groups),
diff --git a/paperless-backend/src/barcode/barcode-scanner.service.ts b/paperless-backend/src/barcode/barcode-scanner.service.ts
index 11a57d2..4f335de 100644
--- a/paperless-backend/src/barcode/barcode-scanner.service.ts
+++ b/paperless-backend/src/barcode/barcode-scanner.service.ts
@@ -2,7 +2,7 @@ import { Injectable, Logger, OnApplicationBootstrap } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import * as fs from 'fs/promises';
-import sharp = require('sharp');
+import sharp from 'sharp';
 import { PdfService } from '../preprocessing/pdf.service';
 import { QrCodeService } from '../preprocessing/qr-code.service';
 import {
@@ -18,6 +18,7 @@ import {
   applyTemplate,
   buildVariables,
 } from '../inbox-postprocessor/variable-resolver';
+import { getErrorMessage } from '../common/error.util';
 
 export interface MatchedBarcode {
   page: number;
@@ -56,9 +57,9 @@ export class BarcodeScannerService implements OnApplicationBootstrap {
     let rows: BarcodeTemplate[];
     try {
       rows = await this.templateRepo.find();
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.warn(
-        `Template-Migration: Query fehlgeschlagen: ${err.message}`,
+        `Template-Migration: Query fehlgeschlagen: ${getErrorMessage(err)}`,
       );
       return;
     }
@@ -94,9 +95,9 @@ export class BarcodeScannerService implements OnApplicationBootstrap {
     doc.IsScanned = true;
     try {
       await this.documentRepo.save(doc);
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.warn(
-        `Scan-Ergebnis konnte nicht gespeichert werden (${doc.Id}): ${err.message}`,
+        `Scan-Ergebnis konnte nicht gespeichert werden (${doc.Id}): ${getErrorMessage(err)}`,
       );
     }
 
@@ -192,9 +193,9 @@ export class BarcodeScannerService implements OnApplicationBootstrap {
               qrCodes.push({ page: i + 1, value: qr.data });
             }
           }
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.warn(
-            `QR-Scan fehlgeschlagen (${pdfPath}, Seite ${i + 1}): ${err.message}`,
+            `QR-Scan fehlgeschlagen (${pdfPath}, Seite ${i + 1}): ${getErrorMessage(err)}`,
           );
         }
       }
@@ -203,8 +204,10 @@ export class BarcodeScannerService implements OnApplicationBootstrap {
       await this.pageCache.generate(documentId, images);
 
       return { qrCodes, pageCount: images.length };
-    } catch (err: any) {
-      this.logger.warn(`Kein QR-Scan möglich für ${pdfPath}: ${err.message}`);
+    } catch (err: unknown) {
+      this.logger.warn(
+        `Kein QR-Scan möglich für ${pdfPath}: ${getErrorMessage(err)}`,
+      );
       return { qrCodes: [], pageCount: 0 };
     } finally {
       await this.pdfService.cleanup(images);
@@ -280,8 +283,10 @@ export class BarcodeScannerService implements OnApplicationBootstrap {
     let docs: InboxDocument[];
     try {
       docs = await this.documentRepo.find();
-    } catch (err: any) {
-      this.logger.warn(`Rescan: DB-Query fehlgeschlagen: ${err.message}`);
+    } catch (err: unknown) {
+      this.logger.warn(
+        `Rescan: DB-Query fehlgeschlagen: ${getErrorMessage(err)}`,
+      );
       return { scanned: 0, failed: 0 };
     }
     if (docs.length === 0) return { scanned: 0, failed: 0 };
@@ -306,8 +311,10 @@ export class BarcodeScannerService implements OnApplicationBootstrap {
         doc.PageCount = pageCount;
         await this.documentRepo.save(doc);
         scanned++;
-      } catch (err: any) {
-        this.logger.warn(`Rescan fehlgeschlagen für ${doc.Id}: ${err.message}`);
+      } catch (err: unknown) {
+        this.logger.warn(
+          `Rescan fehlgeschlagen für ${doc.Id}: ${getErrorMessage(err)}`,
+        );
         failed++;
       }
     }
diff --git a/paperless-backend/src/barcode/page-cache.service.ts b/paperless-backend/src/barcode/page-cache.service.ts
index 32c5c9a..be3725e 100644
--- a/paperless-backend/src/barcode/page-cache.service.ts
+++ b/paperless-backend/src/barcode/page-cache.service.ts
@@ -3,6 +3,7 @@ import { ConfigService } from '@nestjs/config';
 import * as path from 'path';
 import * as fs from 'fs/promises';
 import sharp from 'sharp';
+import { getErrorMessage } from '../common/error.util';
 
 const THUMBNAIL_WIDTH = 180;
 
@@ -54,9 +55,9 @@ export class PageCacheService {
           .resize({ width: THUMBNAIL_WIDTH })
           .png()
           .toFile(thumbDest);
-      } catch (err: any) {
+      } catch (err: unknown) {
         this.logger.warn(
-          `Seiten-Cache fehlgeschlagen (${documentId} Seite ${page}): ${err.message}`,
+          `Seiten-Cache fehlgeschlagen (${documentId} Seite ${page}): ${getErrorMessage(err)}`,
         );
       }
     }
@@ -103,9 +104,9 @@ export class PageCacheService {
         const to = path.join(dir, `page-${n - 1}.${variant}.png`);
         try {
           await fs.rename(from, to);
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.warn(
-            `Cache-Shift fehlgeschlagen (${documentId} Seite ${n} ${variant}): ${err.message}`,
+            `Cache-Shift fehlgeschlagen (${documentId} Seite ${n} ${variant}): ${getErrorMessage(err)}`,
           );
         }
       }
diff --git a/paperless-backend/src/common/error.util.ts b/paperless-backend/src/common/error.util.ts
new file mode 100644
index 0000000..1b97a5a
--- /dev/null
+++ b/paperless-backend/src/common/error.util.ts
@@ -0,0 +1,55 @@
+/**
+ * Hilfsfunktionen, um in catch-Blöcken sicher auf Fehlerwerte vom Typ
+ * `unknown` zuzugreifen, statt unsichere `any`-Zugriffe zu verwenden.
+ */
+
+/** Extrahiert eine lesbare Fehlermeldung aus einem unbekannten Fehlerwert. */
+export function getErrorMessage(err: unknown): string {
+  if (err instanceof Error) return err.message;
+  if (typeof err === 'string') return err;
+  if (
+    err !== null &&
+    typeof err === 'object' &&
+    'message' in err &&
+    typeof (err as { message: unknown }).message === 'string'
+  ) {
+    return (err as { message: string }).message;
+  }
+  return String(err);
+}
+
+/** Liefert den Stacktrace, falls es sich um ein Error-Objekt handelt. */
+export function getErrorStack(err: unknown): string | undefined {
+  return err instanceof Error ? err.stack : undefined;
+}
+
+/**
+ * Liefert `err.response.data` eines HTTP-Fehlers (z. B. von axios), falls
+ * vorhanden — ohne den Fehlerwert als `any` zu behandeln.
+ */
+export function getResponseData(err: unknown): unknown {
+  if (
+    err !== null &&
+    typeof err === 'object' &&
+    'response' in err &&
+    (err as { response: unknown }).response !== null &&
+    typeof (err as { response: unknown }).response === 'object'
+  ) {
+    const response = (err as { response: Record<string, unknown> }).response;
+    return 'data' in response ? response.data : undefined;
+  }
+  return undefined;
+}
+
+/** Liefert den Node-Fehlercode (z. B. 'ENOENT', 'EXDEV'), falls vorhanden. */
+export function getErrorCode(err: unknown): string | undefined {
+  if (
+    err !== null &&
+    typeof err === 'object' &&
+    'code' in err &&
+    typeof (err as { code: unknown }).code === 'string'
+  ) {
+    return (err as { code: string }).code;
+  }
+  return undefined;
+}
diff --git a/paperless-backend/src/daily-digest/daily-digest.controller.ts b/paperless-backend/src/daily-digest/daily-digest.controller.ts
index 936fe9d..8e409e4 100644
--- a/paperless-backend/src/daily-digest/daily-digest.controller.ts
+++ b/paperless-backend/src/daily-digest/daily-digest.controller.ts
@@ -1,5 +1,7 @@
 import { Controller, Post, Request, HttpCode } from '@nestjs/common';
 import { DailyDigestService } from './daily-digest.service';
+import type { AuthenticatedRequest } from '../auth/authenticated-request';
+import { getErrorMessage } from '../common/error.util';
 
 @Controller('api/daily-digest')
 export class DailyDigestController {
@@ -7,8 +9,8 @@ export class DailyDigestController {
 
   @Post('send-now')
   @HttpCode(200)
-  async sendNow(@Request() req: any) {
-    const { userId, email, preferredUsername, groups } = req.user;
+  async sendNow(@Request() req: AuthenticatedRequest) {
+    const { userId, email, preferredUsername, groups } = req.user!;
     if (!email) {
       return {
         ok: false,
@@ -19,12 +21,12 @@ export class DailyDigestController {
       await this.dailyDigestService.sendDigestForUser(
         userId,
         email,
-        preferredUsername,
+        preferredUsername ?? undefined,
         groups,
       );
       return { ok: true };
-    } catch (err: any) {
-      return { ok: false, error: err.message };
+    } catch (err: unknown) {
+      return { ok: false, error: getErrorMessage(err) };
     }
   }
 }
diff --git a/paperless-backend/src/email-download/email-download.service.ts b/paperless-backend/src/email-download/email-download.service.ts
index a21283d..cd0cb65 100644
--- a/paperless-backend/src/email-download/email-download.service.ts
+++ b/paperless-backend/src/email-download/email-download.service.ts
@@ -19,6 +19,7 @@ import { Email } from '../database/entities/email.entity';
 import { Attachment } from '../database/entities/attachment.entity';
 import { Content } from '../database/entities/content.entity';
 import { isERechnung } from './zugferd.util';
+import { getErrorMessage, getErrorStack } from '../common/error.util';
 
 @Injectable()
 export class EmailDownloadService {
@@ -45,10 +46,10 @@ export class EmailDownloadService {
     this.running = true;
     try {
       await this.fetchAndStore();
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.error(
-        `Fehler im E-Mail-Download-Job: ${err.message}`,
-        err.stack,
+        `Fehler im E-Mail-Download-Job: ${getErrorMessage(err)}`,
+        getErrorStack(err),
       );
     } finally {
       this.running = false;
@@ -116,10 +117,10 @@ export class EmailDownloadService {
           }
 
           await this.processMessage(msg);
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.error(
-            `Fehler beim Abrufen der Nachricht ${messageId}: ${err.message}`,
-            err.stack,
+            `Fehler beim Abrufen der Nachricht ${messageId}: ${getErrorMessage(err)}`,
+            getErrorStack(err),
           );
         }
       }
@@ -157,7 +158,7 @@ export class EmailDownloadService {
     }> = [];
 
     for (const att of parsed.attachments) {
-      const entry = await this.buildAttachment(att);
+      const entry = this.buildAttachment(att);
       if (entry) attachmentsToPersist.push(entry);
     }
 
@@ -214,9 +215,9 @@ export class EmailDownloadService {
 
       await this.pdfService.cleanup(images);
       await fs.unlink(tempPdfPath).catch(() => {});
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.warn(
-        `Konnte Vorschaubilder für Anhang ${attachment.Id} nicht generieren: ${err.message}`,
+        `Konnte Vorschaubilder für Anhang ${attachment.Id} nicht generieren: ${getErrorMessage(err)}`,
       );
     }
   }
@@ -262,9 +263,9 @@ export class EmailDownloadService {
     return { processed, failed };
   }
 
-  private async buildAttachment(
+  private buildAttachment(
     att: MailAttachment,
-  ): Promise<{ attachment: Attachment; buffer: Buffer } | null> {
+  ): { attachment: Attachment; buffer: Buffer } | null {
     const buffer = att.content;
     if (!Buffer.isBuffer(buffer) || buffer.length === 0) return null;
 
diff --git a/paperless-backend/src/email/email-import.controller.ts b/paperless-backend/src/email/email-import.controller.ts
index 7555c60..f847386 100644
--- a/paperless-backend/src/email/email-import.controller.ts
+++ b/paperless-backend/src/email/email-import.controller.ts
@@ -16,6 +16,7 @@ import { EmailImportService } from './email-import.service';
 import { EmailPageCacheService } from './email-page-cache.service';
 import { RequirePermissions } from '../auth/permissions.decorator';
 import { Permission } from '../auth/permissions.enum';
+import { getErrorMessage } from '../common/error.util';
 
 @Controller('api/email-import')
 export class EmailImportController {
@@ -131,9 +132,14 @@ export class EmailImportController {
         `inline; filename="preview-${attachmentId}.pdf"`,
       );
       res.send(pdfBuffer);
-    } catch (err: any) {
-      this.logger.error(`Error generating print preview: ${err.message}`);
-      throw new HttpException(err.message, HttpStatus.INTERNAL_SERVER_ERROR);
+    } catch (err: unknown) {
+      this.logger.error(
+        `Error generating print preview: ${getErrorMessage(err)}`,
+      );
+      throw new HttpException(
+        getErrorMessage(err),
+        HttpStatus.INTERNAL_SERVER_ERROR,
+      );
     }
   }
 
@@ -185,9 +191,12 @@ export class EmailImportController {
     try {
       const result = await this.importService.executeImport(importData);
       return result;
-    } catch (err: any) {
-      this.logger.error(`Error executing import: ${err.message}`);
-      throw new HttpException(err.message, HttpStatus.INTERNAL_SERVER_ERROR);
+    } catch (err: unknown) {
+      this.logger.error(`Error executing import: ${getErrorMessage(err)}`);
+      throw new HttpException(
+        getErrorMessage(err),
+        HttpStatus.INTERNAL_SERVER_ERROR,
+      );
     }
   }
 }
diff --git a/paperless-backend/src/email/email-import.service.ts b/paperless-backend/src/email/email-import.service.ts
index 022b167..2431c00 100644
--- a/paperless-backend/src/email/email-import.service.ts
+++ b/paperless-backend/src/email/email-import.service.ts
@@ -17,6 +17,7 @@ import * as path from 'path';
 import * as os from 'os';
 import * as fs from 'fs/promises';
 import * as crypto from 'crypto';
+import { getErrorMessage } from '../common/error.util';
 
 @Injectable()
 export class EmailImportService {
@@ -80,9 +81,9 @@ export class EmailImportService {
           await this.attachmentRepo.save(attachment);
 
           await this.pdfService.cleanup(images);
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.warn(
-            `Fehler bei on-demand Vorschau-Generierung für Anhang ${attachment.Id}: ${err.message}`,
+            `Fehler bei on-demand Vorschau-Generierung für Anhang ${attachment.Id}: ${getErrorMessage(err)}`,
           );
         } finally {
           await fs.unlink(tempPdfPath).catch(() => {});
@@ -156,11 +157,12 @@ export class EmailImportService {
 
       this.logger.debug(`Received Belegnummer: ${result}`);
       return String(result);
-    } catch (error: any) {
-      const status = error.response?.status || 'UNKNOWN';
-      const detail = error.response?.data
-        ? JSON.stringify(error.response.data)
-        : error.message;
+    } catch (error: unknown) {
+      const axiosErr = axios.isAxiosError(error) ? error : undefined;
+      const status = axiosErr?.response?.status ?? 'UNKNOWN';
+      const detail = axiosErr?.response?.data
+        ? JSON.stringify(axiosErr.response.data)
+        : getErrorMessage(error);
       this.logger.error(
         `Failed to fetch Belegnummer from ${url}. Status: ${status}, Detail: ${detail}`,
       );
@@ -191,9 +193,9 @@ export class EmailImportService {
         `Releasing Belegnummer: ${cleanNumber} (original: ${number}) via ${url}`,
       );
       await axios.get(url);
-    } catch (error: any) {
+    } catch (error: unknown) {
       this.logger.error(
-        `Failed to release Belegnummer at ${url}: ${error.message}`,
+        `Failed to release Belegnummer at ${url}: ${getErrorMessage(error)}`,
       );
     }
   }
@@ -215,9 +217,9 @@ export class EmailImportService {
         `Setting Belegnummer: ${cleanNumber} (original: ${number}) via ${url}`,
       );
       await axios.get(url);
-    } catch (error: any) {
+    } catch (error: unknown) {
       this.logger.error(
-        `Failed to set Belegnummer at ${url}: ${error.message}`,
+        `Failed to set Belegnummer at ${url}: ${getErrorMessage(error)}`,
       );
       throw new HttpException(
         'Fehler beim Setzen der Belegnummer',
@@ -610,7 +612,9 @@ export class EmailImportService {
                 docId = statusObj.related_document;
                 break;
               }
-            } catch (e) {}
+            } catch {
+              // Task-Status nicht parsebar: nächsten Versuch abwarten
+            }
           }
 
           if (docId) {
@@ -629,7 +633,10 @@ export class EmailImportService {
         // Confirm Belegnummer if used
         if (att.belegnummer && att.barcode?.nummer) {
           await this.setBelegnummer(data.emailDate, att.barcode.nummer).catch(
-            (e) => this.logger.warn(`Failed to set Belegnummer: ${e.message}`),
+            (e) =>
+              this.logger.warn(
+                `Failed to set Belegnummer: ${getErrorMessage(e)}`,
+              ),
           );
         }
 
diff --git a/paperless-backend/src/email/email-page-cache.service.ts b/paperless-backend/src/email/email-page-cache.service.ts
index 80f8ff0..fc8849f 100644
--- a/paperless-backend/src/email/email-page-cache.service.ts
+++ b/paperless-backend/src/email/email-page-cache.service.ts
@@ -3,6 +3,7 @@ import { ConfigService } from '@nestjs/config';
 import * as path from 'path';
 import * as fs from 'fs/promises';
 import sharp from 'sharp';
+import { getErrorMessage } from '../common/error.util';
 
 const THUMBNAIL_WIDTH = 180;
 
@@ -55,9 +56,9 @@ export class EmailPageCacheService {
           .resize({ width: THUMBNAIL_WIDTH })
           .png()
           .toFile(thumbDest);
-      } catch (err: any) {
+      } catch (err: unknown) {
         this.logger.warn(
-          `E-Mail Page Cache fehlgeschlagen (Attachment ${attachmentId} Seite ${page}): ${err.message}`,
+          `E-Mail Page Cache fehlgeschlagen (Attachment ${attachmentId} Seite ${page}): ${getErrorMessage(err)}`,
         );
       }
     }
diff --git a/paperless-backend/src/email/email.controller.ts b/paperless-backend/src/email/email.controller.ts
index dc18b9b..213b78a 100644
--- a/paperless-backend/src/email/email.controller.ts
+++ b/paperless-backend/src/email/email.controller.ts
@@ -19,6 +19,7 @@ import { Content } from '../database/entities/content.entity';
 import { PaperlessService } from '../paperless/paperless.service';
 import { RequirePermissions } from '../auth/permissions.decorator';
 import { Permission } from '../auth/permissions.enum';
+import { getErrorMessage, getErrorStack } from '../common/error.util';
 
 @Controller('api/emails')
 export class EmailController {
@@ -173,10 +174,10 @@ export class EmailController {
                   );
                 }
               }
-            } catch (err: any) {
+            } catch (err: unknown) {
               this.logger.error(
-                `Fehler bei Checksummen-Prüfung für Attachment ${attachment.Id}: ${err.message}`,
-                err.stack,
+                `Fehler bei Checksummen-Prüfung für Attachment ${attachment.Id}: ${getErrorMessage(err)}`,
+                getErrorStack(err),
               );
             }
           }
@@ -203,10 +204,10 @@ export class EmailController {
         `Prüfung abgeschlossen. ${updatedCount} E-Mails aktualisiert, ${idsUpdated} Paperless-IDs ergänzt, ${skippedCount} übersprungen.`,
       );
       return { updatedCount, idsUpdated };
-    } catch (error: any) {
+    } catch (error: unknown) {
       this.logger.error(
-        `Kritischer Fehler bei checkAttachments: ${error.message}`,
-        error.stack,
+        `Kritischer Fehler bei checkAttachments: ${getErrorMessage(error)}`,
+        getErrorStack(error),
       );
       throw error;
     }
diff --git a/paperless-backend/src/freigabe/freigabe.service.ts b/paperless-backend/src/freigabe/freigabe.service.ts
index f0562a8..d0d361f 100644
--- a/paperless-backend/src/freigabe/freigabe.service.ts
+++ b/paperless-backend/src/freigabe/freigabe.service.ts
@@ -48,7 +48,7 @@ export class FreigabeService {
     try {
       const result = await this.paperlessService.getDocuments(params);
       return result;
-    } catch (err: any) {
+    } catch {
       // Fallback: Paperless unterstützt den custom_fields-Filter möglicherweise nicht
       // In diesem Fall alle Belege laden und client-seitig filtern
       this.logger.warn(
diff --git a/paperless-backend/src/inbox-postprocessor/inbox-postprocessor.service.ts b/paperless-backend/src/inbox-postprocessor/inbox-postprocessor.service.ts
index 2704547..27912af 100644
--- a/paperless-backend/src/inbox-postprocessor/inbox-postprocessor.service.ts
+++ b/paperless-backend/src/inbox-postprocessor/inbox-postprocessor.service.ts
@@ -18,6 +18,7 @@ import {
   extractSectionToTemp,
 } from './edit-applier';
 import { applyTemplate, buildVariables } from './variable-resolver';
+import { getErrorMessage } from '../common/error.util';
 
 function parseFlexDate(s: string): Date | null {
   if (!s) return null;
@@ -276,16 +277,16 @@ export class InboxPostprocessorService {
                   abortProcessing = true;
                   break;
                 }
-              } catch (err: any) {
+              } catch (err: unknown) {
                 this.logger.error(
-                  `Aktion PAPERLESS#${action.Id} für Dokument ${doc.Id} fehlgeschlagen: ${err.message}`,
+                  `Aktion PAPERLESS#${action.Id} für Dokument ${doc.Id} fehlgeschlagen: ${getErrorMessage(err)}`,
                 );
                 results.push({
                   sectionIndex: currentSectionIndex,
                   actionId: action.Id,
                   actionType: action.ActionType,
                   ok: false,
-                  message: err.message,
+                  message: getErrorMessage(err),
                 });
               }
             } else {
@@ -303,16 +304,16 @@ export class InboxPostprocessorService {
                   actionType: action.ActionType,
                   ok: true,
                 });
-              } catch (err: any) {
+              } catch (err: unknown) {
                 this.logger.error(
-                  `Aktion ${action.ActionType}#${action.Id} für Dokument ${doc.Id} fehlgeschlagen: ${err.message}`,
+                  `Aktion ${action.ActionType}#${action.Id} für Dokument ${doc.Id} fehlgeschlagen: ${getErrorMessage(err)}`,
                 );
                 results.push({
                   sectionIndex: currentSectionIndex,
                   actionId: action.Id,
                   actionType: action.ActionType,
                   ok: false,
-                  message: err.message,
+                  message: getErrorMessage(err),
                 });
               }
             }
diff --git a/paperless-backend/src/inbox-postprocessor/variable-resolver.ts b/paperless-backend/src/inbox-postprocessor/variable-resolver.ts
index d72c4c2..c04b8b3 100644
--- a/paperless-backend/src/inbox-postprocessor/variable-resolver.ts
+++ b/paperless-backend/src/inbox-postprocessor/variable-resolver.ts
@@ -48,7 +48,9 @@ export function buildVariables(ctx: ResolverContext): Record<string, string> {
           if (gv !== undefined) vars[`barcode.${sanitizeKey(g)}`] = gv;
         }
       }
-    } catch {}
+    } catch {
+      // Ungültige Regex/Barcode-Daten: Variablen bleiben ungesetzt
+    }
   }
 
   return vars;
diff --git a/paperless-backend/src/inbox/clients.controller.ts b/paperless-backend/src/inbox/clients.controller.ts
index 8baa58b..81e8483 100644
--- a/paperless-backend/src/inbox/clients.controller.ts
+++ b/paperless-backend/src/inbox/clients.controller.ts
@@ -3,6 +3,7 @@ import { InjectRepository } from '@nestjs/typeorm';
 import { Repository, In } from 'typeorm';
 import { Client } from '../database/entities/client.entity';
 import { UserClient } from '../database/entities/user-client.entity';
+import type { AuthenticatedRequest } from '../auth/authenticated-request';
 
 @Controller('api/clients')
 export class ClientsController {
@@ -15,8 +16,8 @@ export class ClientsController {
   ) {}
 
   @Get()
-  async getMyClients(@Request() req: any) {
-    const userId = req.user.userId;
+  async getMyClients(@Request() req: AuthenticatedRequest) {
+    const userId = req.user!.userId;
     const mappings = await this.userClientRepo.find({
       where: { UserId: userId },
     });
diff --git a/paperless-backend/src/inbox/inbox-migration.service.ts b/paperless-backend/src/inbox/inbox-migration.service.ts
index 737e1d2..1590b73 100644
--- a/paperless-backend/src/inbox/inbox-migration.service.ts
+++ b/paperless-backend/src/inbox/inbox-migration.service.ts
@@ -10,6 +10,7 @@ import {
   type InboxSource,
   type StoredQrCode,
 } from '../database/entities/inbox-document.entity';
+import { getErrorMessage, getErrorCode } from '../common/error.util';
 import { PageCacheService } from '../barcode/page-cache.service';
 
 interface LegacyScanRow {
@@ -41,10 +42,10 @@ export class InboxMigrationService implements OnApplicationBootstrap {
         withFileTypes: true,
       });
       subdirs = entries.filter((e) => e.isDirectory()).map((e) => e.name);
-    } catch (err: any) {
-      if (err.code !== 'ENOENT') {
+    } catch (err: unknown) {
+      if (getErrorCode(err) !== 'ENOENT') {
         this.logger.warn(
-          `Migration: ${this.legacyRoot} nicht lesbar: ${err.message}`,
+          `Migration: ${this.legacyRoot} nicht lesbar: ${getErrorMessage(err)}`,
         );
       }
       return;
@@ -56,8 +57,10 @@ export class InboxMigrationService implements OnApplicationBootstrap {
       let files: string[];
       try {
         files = await fs.readdir(dir);
-      } catch (err: any) {
-        this.logger.warn(`Migration: ${dir} nicht lesbar: ${err.message}`);
+      } catch (err: unknown) {
+        this.logger.warn(
+          `Migration: ${dir} nicht lesbar: ${getErrorMessage(err)}`,
+        );
         continue;
       }
 
@@ -67,9 +70,9 @@ export class InboxMigrationService implements OnApplicationBootstrap {
         try {
           await this.migrateFile(src, subdir, name);
           migrated += 1;
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.error(
-            `Migration fehlgeschlagen (${src}): ${err.message}`,
+            `Migration fehlgeschlagen (${src}): ${getErrorMessage(err)}`,
           );
         }
       }
@@ -116,8 +119,8 @@ export class InboxMigrationService implements OnApplicationBootstrap {
     try {
       await fs.rename(src, dest);
       return;
-    } catch (err: any) {
-      if (err.code !== 'EXDEV') throw err;
+    } catch (err: unknown) {
+      if (getErrorCode(err) !== 'EXDEV') throw err;
     }
     await fs.copyFile(src, dest);
     try {
diff --git a/paperless-backend/src/inbox/inbox.controller.ts b/paperless-backend/src/inbox/inbox.controller.ts
index 34a97d4..558b0a3 100644
--- a/paperless-backend/src/inbox/inbox.controller.ts
+++ b/paperless-backend/src/inbox/inbox.controller.ts
@@ -21,6 +21,8 @@ import { BarcodeScannerService } from '../barcode/barcode-scanner.service';
 import { UserSettingsService } from '../user-settings/user-settings.service';
 import { RequirePermissions } from '../auth/permissions.decorator';
 import { Permission } from '../auth/permissions.enum';
+import type { AuthenticatedRequest } from '../auth/authenticated-request';
+import type { InboxSource } from '../database/entities/inbox-document.entity';
 
 @Controller('api/inbox')
 @RequirePermissions(Permission.VIEW_SCANNER)
@@ -33,7 +35,7 @@ export class InboxController {
   ) {}
 
   @Get()
-  async list(@Request() req: any) {
+  async list(@Request() req: AuthenticatedRequest) {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
     return this.inboxService.listFiles(preferredUsername);
@@ -47,7 +49,7 @@ export class InboxController {
   @Get(':id/preview')
   async preview(
     @Param('id') id: string,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
     @Res({ passthrough: true }) res: Response,
   ): Promise<StreamableFile> {
     const preferredUsername: string | null =
@@ -69,7 +71,7 @@ export class InboxController {
   async pageThumbnail(
     @Param('id') id: string,
     @Param('page', ParseIntPipe) page: number,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
     @Res({ passthrough: true }) res: Response,
   ): Promise<StreamableFile> {
     const preferredUsername: string | null =
@@ -88,7 +90,10 @@ export class InboxController {
 
   @Delete(':id')
   @HttpCode(204)
-  async remove(@Param('id') id: string, @Request() req: any): Promise<void> {
+  async remove(
+    @Param('id') id: string,
+    @Request() req: AuthenticatedRequest,
+  ): Promise<void> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
     await this.inboxService.deleteDocument(id, preferredUsername);
@@ -99,7 +104,7 @@ export class InboxController {
   async removePage(
     @Param('id') id: string,
     @Param('page', ParseIntPipe) page: number,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
   ): Promise<void> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
@@ -111,7 +116,7 @@ export class InboxController {
   async toggleManualSplit(
     @Param('id') id: string,
     @Param('page', ParseIntPipe) page: number,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
   ): Promise<void> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
@@ -122,7 +127,7 @@ export class InboxController {
   @HttpCode(204)
   async resetEdits(
     @Param('id') id: string,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
   ): Promise<void> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
@@ -132,7 +137,7 @@ export class InboxController {
   @Post(':id/postprocess')
   async postprocess(
     @Param('id') id: string,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
     @Body()
     body: {
       sectionOffset?: number;
@@ -158,7 +163,7 @@ export class InboxController {
     @Param('id') id: string,
     @Param('page', ParseIntPipe) page: number,
     @Body() body: { rotation?: number },
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
   ): Promise<void> {
     const rotation = Number(body?.rotation);
     if (!Number.isFinite(rotation)) {
@@ -178,7 +183,7 @@ export class InboxController {
   async pagePreview(
     @Param('id') id: string,
     @Param('page', ParseIntPipe) page: number,
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
     @Res({ passthrough: true }) res: Response,
   ): Promise<StreamableFile> {
     const preferredUsername: string | null =
@@ -200,7 +205,7 @@ export class InboxController {
     @Param('id') id: string,
     @Param('page', ParseIntPipe) page: number,
     @Body() body: { x: number; y: number; w: number; h: number },
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
   ): Promise<{ found: string[] }> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
@@ -219,8 +224,8 @@ export class InboxController {
   @HttpCode(204)
   async updateSource(
     @Param('id') id: string,
-    @Body() body: { source: any },
-    @Request() req: any,
+    @Body() body: { source: InboxSource },
+    @Request() req: AuthenticatedRequest,
   ): Promise<void> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
@@ -231,7 +236,7 @@ export class InboxController {
   async downloadSegment(
     @Param('id') id: string,
     @Body() body: { pages: number[] },
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
     @Res({ passthrough: true }) res: Response,
   ): Promise<StreamableFile> {
     const preferredUsername: string | null =
@@ -263,13 +268,13 @@ export class InboxController {
       segments: { pages: number[]; filename: string }[];
       sender?: string;
     },
-    @Request() req: any,
+    @Request() req: AuthenticatedRequest,
   ): Promise<void> {
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
     const smtpOverride =
       body.sender === 'user'
-        ? await this.userSettingsService.getSmtpConfig(req.user.userId)
+        ? await this.userSettingsService.getSmtpConfig(req.user!.userId)
         : null;
     await this.inboxService.sendAsEmail(id, preferredUsername, {
       ...body,
diff --git a/paperless-backend/src/inbox/inbox.service.ts b/paperless-backend/src/inbox/inbox.service.ts
index cdba0ab..fb3e2e0 100644
--- a/paperless-backend/src/inbox/inbox.service.ts
+++ b/paperless-backend/src/inbox/inbox.service.ts
@@ -19,6 +19,7 @@ import {
 } from '../database/entities/inbox-document.entity';
 import { MailService } from '../postprocessing/mail.service';
 import { buildSegmentBuffer } from '../inbox-postprocessor/edit-applier';
+import { getErrorMessage } from '../common/error.util';
 
 export interface InboxFile {
   id: string;
@@ -99,9 +100,9 @@ export class InboxService {
     try {
       const stat = await fs.stat(pdfPath);
       if (!stat.isFile()) throw new Error('not a file');
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.warn(
-        `Datei fehlt trotz DB-Eintrag (${doc.Id}): ${err.message}`,
+        `Datei fehlt trotz DB-Eintrag (${doc.Id}): ${getErrorMessage(err)}`,
       );
       throw new NotFoundException('Dokument nicht gefunden');
     }
@@ -218,9 +219,9 @@ export class InboxService {
     await this.documentRepo.delete(doc.Id);
     try {
       await fs.rm(dir, { recursive: true, force: true });
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.warn(
-        `Dokument-Ordner konnte nicht gelöscht werden (${dir}): ${err.message}`,
+        `Dokument-Ordner konnte nicht gelöscht werden (${dir}): ${getErrorMessage(err)}`,
       );
     }
   }
diff --git a/paperless-backend/src/kontonummern/kontonummern.service.ts b/paperless-backend/src/kontonummern/kontonummern.service.ts
index d9422dc..ae65f2a 100644
--- a/paperless-backend/src/kontonummern/kontonummern.service.ts
+++ b/paperless-backend/src/kontonummern/kontonummern.service.ts
@@ -1,4 +1,4 @@
-import { Injectable, NotFoundException } from '@nestjs/common';
+import { Injectable } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { Kontonummer } from '../database/entities';
diff --git a/paperless-backend/src/label-print-agent/label-print-agent.service.ts b/paperless-backend/src/label-print-agent/label-print-agent.service.ts
index 617bba2..a8f26c1 100644
--- a/paperless-backend/src/label-print-agent/label-print-agent.service.ts
+++ b/paperless-backend/src/label-print-agent/label-print-agent.service.ts
@@ -10,6 +10,7 @@ import { Subject, Observable } from 'rxjs';
 import { LabelPrintJob } from '../database/entities/label-print-job.entity';
 import { BarcodeTemplate } from '../database/entities/barcode-template.entity';
 import { LabelRendererService } from './label-renderer.service';
+import { getErrorMessage } from '../common/error.util';
 
 function isSafeUrl(url: string): boolean {
   try {
@@ -95,8 +96,10 @@ export class LabelPrintAgentService {
           const res = await fetch(url);
           const text = (await res.text()).trim();
           vars['number'] = text;
-        } catch (err: any) {
-          this.logger.warn(`GET-URL fehlgeschlagen (${url}): ${err.message}`);
+        } catch (err: unknown) {
+          this.logger.warn(
+            `GET-URL fehlgeschlagen (${url}): ${getErrorMessage(err)}`,
+          );
         }
       } else {
         this.logger.warn(`GET-URL übersprungen (ungültiges Protokoll): ${url}`);
@@ -149,9 +152,9 @@ export class LabelPrintAgentService {
             candidate.LabelVariables ?? {},
           );
           await this.jobRepo.save(candidate);
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.error(
-            `Label-Rendering fehlgeschlagen für Job ${candidate.Id}: ${err.message}`,
+            `Label-Rendering fehlgeschlagen für Job ${candidate.Id}: ${getErrorMessage(err)}`,
           );
         }
       }
@@ -257,8 +260,10 @@ export class LabelPrintAgentService {
     }
     try {
       await fetch(url, { method: 'POST' });
-    } catch (err: any) {
-      this.logger.warn(`${type}-URL fehlgeschlagen (${url}): ${err.message}`);
+    } catch (err: unknown) {
+      this.logger.warn(
+        `${type}-URL fehlgeschlagen (${url}): ${getErrorMessage(err)}`,
+      );
     }
   }
 }
diff --git a/paperless-backend/src/label-print-agent/label-renderer.service.ts b/paperless-backend/src/label-print-agent/label-renderer.service.ts
index 4dba455..e40cccf 100644
--- a/paperless-backend/src/label-print-agent/label-renderer.service.ts
+++ b/paperless-backend/src/label-print-agent/label-renderer.service.ts
@@ -2,6 +2,7 @@ import { Injectable, Logger } from '@nestjs/common';
 import * as QRCode from 'qrcode';
 import { Resvg } from '@resvg/resvg-js';
 import type { LabelElement } from '../database/entities/barcode-template.entity';
+import { getErrorMessage } from '../common/error.util';
 
 const MM_TO_PX = 300 / 25.4; // 300 DPI
 
@@ -84,9 +85,9 @@ export class LabelRendererService {
           parts.push(
             `<image href="data:image/png;base64,${b64}" x="${x}" y="${y}" width="${size}" height="${size}"/>`,
           );
-        } catch (err: any) {
+        } catch (err: unknown) {
           this.logger.warn(
-            `QR-Code-Rendering fehlgeschlagen für "${content}": ${err.message}`,
+            `QR-Code-Rendering fehlgeschlagen für "${content}": ${getErrorMessage(err)}`,
           );
         }
       } else if (el.type === 'line') {
diff --git a/paperless-backend/src/paperless/paperless-processor.service.ts b/paperless-backend/src/paperless/paperless-processor.service.ts
index 9a54b6f..dbb5442 100644
--- a/paperless-backend/src/paperless/paperless-processor.service.ts
+++ b/paperless-backend/src/paperless/paperless-processor.service.ts
@@ -7,6 +7,7 @@ import { DocumentField } from '../database/entities/document-field.entity';
 import { DocumentType } from '../database/entities/document-type.entity';
 import { PaperlessService } from './paperless.service';
 import { PostprocessingService } from '../postprocessing/postprocessing.service';
+import { getErrorMessage, getResponseData } from '../common/error.util';
 
 @Injectable()
 export class PaperlessProcessorService {
@@ -49,13 +50,14 @@ export class PaperlessProcessorService {
           );
           // Postprocessing nach dem Speichern evaluieren
           await this.postprocessingService.evaluate(updatedDoc || doc);
-        } catch (innerErr: any) {
+        } catch (innerErr: unknown) {
           this.logger.error(
-            `Fehler bei Dokument ID ${doc.id}: ${innerErr.message}`,
+            `Fehler bei Dokument ID ${doc.id}: ${getErrorMessage(innerErr)}`,
           );
-          if (innerErr.response?.data) {
+          const responseData = getResponseData(innerErr);
+          if (responseData) {
             this.logger.error(
-              `Paperless API Response: ${JSON.stringify(innerErr.response.data)}`,
+              `Paperless API Response: ${JSON.stringify(responseData)}`,
             );
           }
         }
diff --git a/paperless-backend/src/paperless/paperless.service.ts b/paperless-backend/src/paperless/paperless.service.ts
index 4a7b33d..ba69dbe 100644
--- a/paperless-backend/src/paperless/paperless.service.ts
+++ b/paperless-backend/src/paperless/paperless.service.ts
@@ -3,7 +3,7 @@ import { ConfigService } from '@nestjs/config';
 import axios, { type AxiosInstance } from 'axios';
 import * as fs from 'fs';
 import * as path from 'path';
-import FormData = require('form-data');
+import FormData from 'form-data';
 
 @Injectable()
 export class PaperlessService {
@@ -133,8 +133,8 @@ export class PaperlessService {
     try {
       const response = await this.client.patch(`/documents/${id}/`, data);
       return response.data;
-    } catch (err: any) {
-      const body = err?.response?.data;
+    } catch (err: unknown) {
+      const body = axios.isAxiosError(err) ? err.response?.data : undefined;
       if (body) {
         this.logger.error(
           `Paperless updateDocument(${id}) Fehlerdetails: ${JSON.stringify(body)}`,
diff --git a/paperless-backend/src/postprocessing/export.service.ts b/paperless-backend/src/postprocessing/export.service.ts
index 2216677..3bf329c 100644
--- a/paperless-backend/src/postprocessing/export.service.ts
+++ b/paperless-backend/src/postprocessing/export.service.ts
@@ -4,6 +4,7 @@ import { Repository } from 'typeorm';
 import { ExportTarget } from '../database/entities/export-target.entity';
 import * as ftp from 'basic-ftp';
 import { createClient, type WebDAVClient } from 'webdav';
+import { getErrorMessage } from '../common/error.util';
 
 @Injectable()
 export class ExportService {
@@ -57,8 +58,8 @@ export class ExportService {
           };
       }
       return { success: true, message: 'Verbindung erfolgreich.' };
-    } catch (err: any) {
-      return { success: false, message: err.message };
+    } catch (err: unknown) {
+      return { success: false, message: getErrorMessage(err) };
     }
   }
 
diff --git a/paperless-backend/src/postprocessing/postprocessing.service.ts b/paperless-backend/src/postprocessing/postprocessing.service.ts
index 5c8d6b0..679fd77 100644
--- a/paperless-backend/src/postprocessing/postprocessing.service.ts
+++ b/paperless-backend/src/postprocessing/postprocessing.service.ts
@@ -13,6 +13,7 @@ import { PaperlessService } from '../paperless/paperless.service';
 import { MailService } from './mail.service';
 import { ExportService } from './export.service';
 import axios from 'axios';
+import { getErrorMessage } from '../common/error.util';
 
 const CACHE_TTL_MS = 5 * 60 * 1000;
 
@@ -91,12 +92,18 @@ export class PostprocessingService {
             'success',
             `Aktion ${action.ActionType} erfolgreich`,
           );
-        } catch (err: any) {
+        } catch (err: unknown) {
           hasError = true;
           this.logger.error(
-            `Fehler bei Aktion ${action.Id} (Typ ${action.ActionType}) für Dokument ${doc.id}: ${err.message}`,
+            `Fehler bei Aktion ${action.Id} (Typ ${action.ActionType}) für Dokument ${doc.id}: ${getErrorMessage(err)}`,
+          );
+          await this.log(
+            rule.Id,
+            action.Id,
+            doc.id,
+            'error',
+            getErrorMessage(err),
           );
-          await this.log(rule.Id, action.Id, doc.id, 'error', err.message);
         }
       }
 
@@ -107,9 +114,9 @@ export class PostprocessingService {
           await this.paperlessService.updateDocument(doc.id, {
             tags: Array.from(currentTags),
           });
-        } catch (tagErr: any) {
+        } catch (tagErr: unknown) {
           this.logger.error(
-            `Konnte Error-Tag ${this.errorTagId} nicht setzen für Dokument ${doc.id}: ${tagErr.message}`,
+            `Konnte Error-Tag ${this.errorTagId} nicht setzen für Dokument ${doc.id}: ${getErrorMessage(tagErr)}`,
           );
         }
       }
@@ -313,8 +320,8 @@ export class PostprocessingService {
         const dt = docTypes.find((x: any) => x.id === doc.document_type);
         doc._documentTypeName = dt?.name ?? '';
       }
-    } catch (err: any) {
-      this.logger.warn(`Konnte Namen nicht auflösen: ${err.message}`);
+    } catch (err: unknown) {
+      this.logger.warn(`Konnte Namen nicht auflösen: ${getErrorMessage(err)}`);
     }
   }
 
diff --git a/paperless-backend/src/preprocessing/document-pipeline.service.ts b/paperless-backend/src/preprocessing/document-pipeline.service.ts
index 5912309..4a7e7ab 100644
--- a/paperless-backend/src/preprocessing/document-pipeline.service.ts
+++ b/paperless-backend/src/preprocessing/document-pipeline.service.ts
@@ -65,8 +65,8 @@ export class DocumentPipelineService {
       }
 
       // 3. OCR auf erster Seite
-      const ocrMarkdown =
-        await this.ocrService.extractTextAsMarkdown(firstPageBuffer);
+      // TODO: OCR-Ergebnis wird aktuell nicht gespeichert/weiterverwendet
+      await this.ocrService.extractTextAsMarkdown(firstPageBuffer);
 
       // 4. Task in DB erstellen
       const year = new Date().getFullYear();
diff --git a/paperless-backend/src/preprocessing/ocr.service.ts b/paperless-backend/src/preprocessing/ocr.service.ts
index 6eb2822..24bffdf 100644
--- a/paperless-backend/src/preprocessing/ocr.service.ts
+++ b/paperless-backend/src/preprocessing/ocr.service.ts
@@ -1,6 +1,7 @@
 import { Injectable, Logger } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 import axios from 'axios';
+import { getErrorMessage } from '../common/error.util';
 
 @Injectable()
 export class OcrService {
@@ -46,8 +47,8 @@ Antworte nur mit dem extrahierten Markdown-Text, keine Erklärungen.`;
         `OCR abgeschlossen: ${markdown.length} Zeichen extrahiert`,
       );
       return markdown;
-    } catch (error: any) {
-      this.logger.error(`Ollama OCR fehlgeschlagen: ${error.message}`);
+    } catch (error: unknown) {
+      this.logger.error(`Ollama OCR fehlgeschlagen: ${getErrorMessage(error)}`);
       throw error;
     }
   }
diff --git a/paperless-backend/src/preprocessing/pdf.service.ts b/paperless-backend/src/preprocessing/pdf.service.ts
index 2baf0f0..9a7c70f 100644
--- a/paperless-backend/src/preprocessing/pdf.service.ts
+++ b/paperless-backend/src/preprocessing/pdf.service.ts
@@ -120,7 +120,9 @@ export class PdfService {
     for (const imgPath of imagePaths) {
       try {
         await fs.unlink(imgPath);
-      } catch {}
+      } catch {
+        // Datei bereits entfernt o. Ä.: ignorieren
+      }
       dirs.add(path.dirname(imgPath));
     }
     for (const dir of dirs) {
diff --git a/paperless-backend/src/preprocessing/qr-code.service.ts b/paperless-backend/src/preprocessing/qr-code.service.ts
index 418496a..2122a8a 100644
--- a/paperless-backend/src/preprocessing/qr-code.service.ts
+++ b/paperless-backend/src/preprocessing/qr-code.service.ts
@@ -1,5 +1,5 @@
 import { Injectable, Logger } from '@nestjs/common';
-import sharp = require('sharp');
+import sharp from 'sharp';
 import jsQR from 'jsqr';
 
 export interface QrCodeResult {
diff --git a/paperless-backend/src/scanner/scanner-watcher.service.ts b/paperless-backend/src/scanner/scanner-watcher.service.ts
index fb59965..f65d065 100644
--- a/paperless-backend/src/scanner/scanner-watcher.service.ts
+++ b/paperless-backend/src/scanner/scanner-watcher.service.ts
@@ -18,6 +18,7 @@ import {
   InboxDocument,
   type InboxSource,
 } from '../database/entities/inbox-document.entity';
+import { getErrorCode, getErrorMessage } from '../common/error.util';
 
 const STABILITY_MS = 5000;
 
@@ -63,7 +64,7 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
     this.logger.log(`Starte Überwachung: ${this.sourceRoot}`);
 
     this.watcher = chokidar.watch(this.sourceRoot, {
-      ignored: /(^|[\/\\])\../,
+      ignored: /(^|[/\\])\../,
       persistent: true,
       ignoreInitial: true,
       awaitWriteFinish: {
@@ -74,9 +75,9 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
     });
 
     this.watcher
-      .on('add', (filePath: string) => this.handleNewFile(filePath))
+      .on('add', (filePath: string) => void this.handleNewFile(filePath))
       .on('error', (error: Error) =>
-        this.logger.error(`Watcher Fehler: ${error.message}`),
+        this.logger.error(`Watcher Fehler: ${getErrorMessage(error)}`),
       );
 
     this.logger.log('Scanner-Watcher aktiv');
@@ -96,10 +97,10 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
         withFileTypes: true,
       });
       subdirs = entries.filter((e) => e.isDirectory()).map((e) => e.name);
-    } catch (err: any) {
+    } catch (err: unknown) {
       if (!silent) {
         this.logger.warn(
-          `Scanner-Check: Quellverzeichnis nicht lesbar (${this.sourceRoot}): ${err.message}`,
+          `Scanner-Check: Quellverzeichnis nicht lesbar (${this.sourceRoot}): ${getErrorMessage(err)}`,
         );
       }
       return;
@@ -111,10 +112,10 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
       let files: string[];
       try {
         files = await fs.readdir(dir);
-      } catch (err: any) {
+      } catch (err: unknown) {
         if (!silent) {
           this.logger.warn(
-            `Scanner-Check: ${dir} nicht lesbar: ${err.message}`,
+            `Scanner-Check: ${dir} nicht lesbar: ${getErrorMessage(err)}`,
           );
         }
         continue;
@@ -151,8 +152,8 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
     this.isPeriodicScanning = true;
     try {
       await this.initialScan(true);
-    } catch (err: any) {
-      this.logger.error(`Periodic Scan Fehler: ${err.message}`);
+    } catch (err: unknown) {
+      this.logger.error(`Periodic Scan Fehler: ${getErrorMessage(err)}`);
     } finally {
       this.isPeriodicScanning = false;
     }
@@ -221,14 +222,14 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
 
       try {
         await this.barcodeScanner.scanAndMatch(doc);
-      } catch (err: any) {
+      } catch (err: unknown) {
         this.logger.warn(
-          `Barcode-Scan nach Move fehlgeschlagen (${id}): ${err.message}`,
+          `Barcode-Scan nach Move fehlgeschlagen (${id}): ${getErrorMessage(err)}`,
         );
       }
-    } catch (err: any) {
+    } catch (err: unknown) {
       this.logger.error(
-        `Übernahme fehlgeschlagen für ${filePath}: ${err.message}`,
+        `Übernahme fehlgeschlagen für ${filePath}: ${getErrorMessage(err)}`,
       );
     } finally {
       this.processing.delete(filePath);
@@ -241,8 +242,10 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
       pending = await this.documentRepo.find({
         where: [{ PageCount: 0 }, { QrCodes: IsNull() }],
       });
-    } catch (err: any) {
-      this.logger.warn(`Backfill: DB-Query fehlgeschlagen: ${err.message}`);
+    } catch (err: unknown) {
+      this.logger.warn(
+        `Backfill: DB-Query fehlgeschlagen: ${getErrorMessage(err)}`,
+      );
       return;
     }
 
@@ -251,8 +254,10 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
       try {
         const didScan = await this.barcodeScanner.ensureScanned(doc);
         if (didScan) scanned += 1;
-      } catch (err: any) {
-        this.logger.warn(`Backfill fehlgeschlagen (${doc.Id}): ${err.message}`);
+      } catch (err: unknown) {
+        this.logger.warn(
+          `Backfill fehlgeschlagen (${doc.Id}): ${getErrorMessage(err)}`,
+        );
       }
     }
 
@@ -267,8 +272,8 @@ export class ScannerWatcherService implements OnModuleInit, OnModuleDestroy {
     try {
       await fs.rename(src, dest);
       return;
-    } catch (err: any) {
-      if (err.code !== 'EXDEV') throw err;
+    } catch (err: unknown) {
+      if (getErrorCode(err) !== 'EXDEV') throw err;
     }
     // Cross-device: copy + unlink. Wenn unlink scheitert, Kopie zurückrollen,
     // damit ein kaputter Mount nicht bei jedem Neustart Duplikate produziert.
diff --git a/paperless-backend/src/settings/settings.controller.ts b/paperless-backend/src/settings/settings.controller.ts
index 67fc92b..e0c7297 100644
--- a/paperless-backend/src/settings/settings.controller.ts
+++ b/paperless-backend/src/settings/settings.controller.ts
@@ -22,10 +22,7 @@ import { PaperlessService } from '../paperless/paperless.service';
 import { Client } from '../database/entities/client.entity';
 import { Setting } from '../database/entities/setting.entity';
 import { CorrespondentSetting } from '../database/entities/correspondent-setting.entity';
-import {
-  InboxPostprocessingAction,
-  type InboxActionType,
-} from '../database/entities/inbox-postprocessing-action.entity';
+import { InboxPostprocessingAction } from '../database/entities/inbox-postprocessing-action.entity';
 import { ExportService } from '../postprocessing/export.service';
 import { RequirePermissions } from '../auth/permissions.decorator';
 import { Permission } from '../auth/permissions.enum';
diff --git a/paperless-backend/src/stats/stats.controller.ts b/paperless-backend/src/stats/stats.controller.ts
index 2074362..7069fb3 100644
--- a/paperless-backend/src/stats/stats.controller.ts
+++ b/paperless-backend/src/stats/stats.controller.ts
@@ -1,12 +1,15 @@
 import { Controller, Get, Request } from '@nestjs/common';
 import { StatsService } from './stats.service';
+import type { AuthenticatedRequest } from '../auth/authenticated-request';
 
 @Controller('api/stats')
 export class StatsController {
   constructor(private readonly statsService: StatsService) {}
 
   @Get('counts')
-  async getCounts(@Request() req: any) {
-    return this.statsService.getDashboardCounts(req.user?.preferredUsername);
+  async getCounts(@Request() req: AuthenticatedRequest) {
+    return this.statsService.getDashboardCounts(
+      req.user?.preferredUsername ?? undefined,
+    );
   }
 }
diff --git a/paperless-backend/src/user-settings/user-settings.controller.ts b/paperless-backend/src/user-settings/user-settings.controller.ts
index fb5105b..ee1d844 100644
--- a/paperless-backend/src/user-settings/user-settings.controller.ts
+++ b/paperless-backend/src/user-settings/user-settings.controller.ts
@@ -7,38 +7,45 @@ import {
   Put,
   Request,
 } from '@nestjs/common';
-import { UserSettingsService } from './user-settings.service';
+import {
+  UserSettingsService,
+  type UpdateUserSettingsInput,
+} from './user-settings.service';
 import { RequirePermissions } from '../auth/permissions.decorator';
 import { Permission } from '../auth/permissions.enum';
+import type { AuthenticatedRequest } from '../auth/authenticated-request';
 
 @Controller('api/user-settings')
 export class UserSettingsController {
   constructor(private readonly userSettingsService: UserSettingsService) {}
 
   @Get()
-  async getSettings(@Request() req: any) {
+  async getSettings(@Request() req: AuthenticatedRequest) {
     return this.userSettingsService.getSettings(
-      req.user.userId,
-      req.user.email,
-      req.user.preferredUsername,
-      req.user.groups,
+      req.user!.userId,
+      req.user!.email,
+      req.user!.preferredUsername ?? undefined,
+      req.user!.groups,
     );
   }
 
   @Put()
-  async updateSettings(@Request() req: any, @Body() body: any) {
+  async updateSettings(
+    @Request() req: AuthenticatedRequest,
+    @Body() body: UpdateUserSettingsInput,
+  ) {
     return this.userSettingsService.updateSettings(
-      req.user.userId,
+      req.user!.userId,
       body,
-      req.user.email,
-      req.user.preferredUsername,
-      req.user.groups,
+      req.user!.email,
+      req.user!.preferredUsername ?? undefined,
+      req.user!.groups,
     );
   }
 
   @Get('senders')
-  async getSenders(@Request() req: any) {
-    return this.userSettingsService.getAvailableSenders(req.user.userId);
+  async getSenders(@Request() req: AuthenticatedRequest) {
+    return this.userSettingsService.getAvailableSenders(req.user!.userId);
   }
 
   @Post('test-smtp')
diff --git a/paperless-backend/src/user-settings/user-settings.service.ts b/paperless-backend/src/user-settings/user-settings.service.ts
index 8afd147..d8104ef 100644
--- a/paperless-backend/src/user-settings/user-settings.service.ts
+++ b/paperless-backend/src/user-settings/user-settings.service.ts
@@ -5,6 +5,7 @@ import { Repository } from 'typeorm';
 import * as nodemailer from 'nodemailer';
 import * as crypto from 'crypto';
 import { UserSettings } from '../database/entities/user-settings.entity';
+import { getErrorMessage } from '../common/error.util';
 
 const ALGORITHM = 'aes-256-gcm';
 
@@ -22,6 +23,20 @@ export interface UserSettingsDto {
   dailyDigestEnabled: boolean;
 }
 
+export interface UpdateUserSettingsInput {
+  smtpHost?: string | null;
+  smtpPort?: number | null;
+  smtpSecure?: boolean;
+  smtpUser?: string | null;
+  smtpPass?: string | null;
+  smtpFrom?: string | null;
+  smtpFromName?: string | null;
+  mailSignatureHtml?: string | null;
+  defaultLabelTemplateId?: number | null;
+  emailRecipientHistory?: string[] | null;
+  dailyDigestEnabled?: boolean;
+}
+
 @Injectable()
 export class UserSettingsService {
   private readonly logger = new Logger(UserSettingsService.name);
@@ -92,19 +107,7 @@ export class UserSettingsService {
 
   async updateSettings(
     userId: string,
-    data: {
-      smtpHost?: string | null;
-      smtpPort?: number | null;
-      smtpSecure?: boolean;
-      smtpUser?: string | null;
-      smtpPass?: string | null;
-      smtpFrom?: string | null;
-      smtpFromName?: string | null;
-      mailSignatureHtml?: string | null;
-      defaultLabelTemplateId?: number | null;
-      emailRecipientHistory?: string[] | null;
-      dailyDigestEnabled?: boolean;
-    },
+    data: UpdateUserSettingsInput,
     email?: string,
     preferredUsername?: string,
     groups?: string[],
@@ -160,8 +163,8 @@ export class UserSettingsService {
     try {
       await transporter.verify();
       return { ok: true };
-    } catch (err: any) {
-      return { ok: false, error: err.message };
+    } catch (err: unknown) {
+      return { ok: false, error: getErrorMessage(err) };
     }
   }
 
diff --git a/paperless-backend/src/webhook/webhook.controller.ts b/paperless-backend/src/webhook/webhook.controller.ts
index 8154711..6b22727 100644
--- a/paperless-backend/src/webhook/webhook.controller.ts
+++ b/paperless-backend/src/webhook/webhook.controller.ts
@@ -20,9 +20,9 @@ export class WebhookController {
   @Public()
   @Post('paperless')
   @HttpCode(HttpStatus.OK)
-  async handlePaperlessWebhook(
-    @Body() payload: PaperlessWebhookPayload,
-  ): Promise<{ status: string }> {
+  handlePaperlessWebhook(@Body() payload: PaperlessWebhookPayload): {
+    status: string;
+  } {
     this.logger.log(
       `Webhook empfangen: action=${payload.action}, document=${payload.document_id}`,
     );
diff --git a/paperless-frontend/eslint.config.js b/paperless-frontend/eslint.config.js
index 5e6b472..ee8c5a9 100644
--- a/paperless-frontend/eslint.config.js
+++ b/paperless-frontend/eslint.config.js
@@ -19,5 +19,19 @@ export default defineConfig([
       ecmaVersion: 2020,
       globals: globals.browser,
     },
+    rules: {
+      // any-getriebene Regel als Warnung (untypisierte Paperless-NGX-API-Daten)
+      '@typescript-eslint/no-explicit-any': 'warn',
+      // Fast-Refresh-Hinweise sind Dev-Komfort, kein Build-Blocker
+      'react-refresh/only-export-components': 'warn',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          argsIgnorePattern: '^_',
+          varsIgnorePattern: '^_',
+          caughtErrors: 'none',
+        },
+      ],
+    },
   },
 ])
diff --git a/paperless-frontend/src/components/DocumentEditModal.tsx b/paperless-frontend/src/components/DocumentEditModal.tsx
index 433c24d..f2c1f8b 100644
--- a/paperless-frontend/src/components/DocumentEditModal.tsx
+++ b/paperless-frontend/src/components/DocumentEditModal.tsx
@@ -121,7 +121,7 @@ export default function DocumentEditModal({ documentId, document, open, onClose,
   useEffect(() => {
     if (open && document) {
         
-        let customFieldsObj: any = {};
+        const customFieldsObj: any = {};
         if (document.customFields) {
            document.customFields.forEach(cf => {
                customFieldsObj[`cf_${cf.field}`] = cf.value;
diff --git a/paperless-frontend/src/components/MailImportWizard.tsx b/paperless-frontend/src/components/MailImportWizard.tsx
index e9465d8..e98c44d 100644
--- a/paperless-frontend/src/components/MailImportWizard.tsx
+++ b/paperless-frontend/src/components/MailImportWizard.tsx
@@ -322,7 +322,9 @@ export default function MailImportWizard({ visible, onClose, onSuccess, email, a
       try {
         const status = await emailImportApi.getJobStatus(jobId);
         if (status?.message) setImportStatus(status.message);
-      } catch {}
+      } catch {
+        // Status-Abfrage fehlgeschlagen: nächsten Poll abwarten
+      }
     }, 1500);
     try {
       const finalData = [];
diff --git a/paperless-frontend/src/pages/SettingsPage.tsx b/paperless-frontend/src/pages/SettingsPage.tsx
index 9e67688..ec84326 100644
--- a/paperless-frontend/src/pages/SettingsPage.tsx
+++ b/paperless-frontend/src/pages/SettingsPage.tsx
@@ -441,9 +441,10 @@ function DocTypeFieldsTable({ docTypeId }: { docTypeId: number }) {
       case 1: return <Tag>Absender</Tag>;
       case 2: return <Tag>Belegdatum</Tag>;
       case 3: return <Tag>Ablagenummer</Tag>;
-      case 4:
+      case 4: {
         const cf = customFields.find(c => c.id === record.TypeIndex);
         return <Tag color="blue">{cf ? cf.name : `CF #${record.TypeIndex}`}</Tag>;
+      }
       case 5: return <Tag>Titel</Tag>;
       default: return <Tag>Unbekannt ({record.Type})</Tag>;
     }
diff --git a/paperless-frontend/src/utils/auth-resource.tsx b/paperless-frontend/src/utils/auth-resource.tsx
index ac5b3d5..1bcaf11 100644
--- a/paperless-frontend/src/utils/auth-resource.tsx
+++ b/paperless-frontend/src/utils/auth-resource.tsx
@@ -8,6 +8,8 @@ export function useAuthUrl(url: string | null | undefined): string | null {
 
   useEffect(() => {
     if (!url) {
+      // Reset des Blob-URLs, wenn keine Quelle (mehr) vorhanden ist
+      // eslint-disable-next-line react-hooks/set-state-in-effect
       setBlobUrl(null);
       return;
     }