feat: auto-move imported emails to IMAP folder and add 90-day cleanup

- New ImapFolderService moves emails to configurable "importiert" folder
  after successful import, creating the folder if it doesn't exist
- Daily cron at 03:00 moves emails older than 90 days to trash and empties it
- Extract createImapClient() helper in EmailDownloadService
- Add ensurePageCache() with in-flight deduplication to BarcodeScannerService
- InboxService regenerates page cache on-demand when image file is missing
- IMAP_IMPORTED_FOLDER and IMAP_TRASH_FOLDER added to .env.example and docker-compose

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

paperless-backend/src/email/email-import.service.ts

@@ -12,6 +12,7 @@ import { Task } from '../database/entities/task.entity';
 import { PaperlessService } from '../paperless/paperless.service';
 import * as QRCode from 'qrcode';
 import { EmailPageCacheService } from './email-page-cache.service';
+import { ImapFolderService } from './imap-folder.service';
 import { PdfService } from '../preprocessing/pdf.service';
 import * as path from 'path';
 import * as os from 'os';
@@ -53,6 +54,7 @@ export class EmailImportService {
     private readonly paperlessService: PaperlessService,
     private readonly pdfService: PdfService,
     private readonly pageCache: EmailPageCacheService,
+    private readonly imapFolderService: ImapFolderService,
   ) {}
 
   async ensurePreviews(emailId: number): Promise<void> {
@@ -653,6 +655,12 @@ export class EmailImportService {
           this.logger.log(
             `Email ${firstAtt.EmailMessageId} als verarbeitet markiert.`,
           );
+          const emailEntity = await this.emailRepo.findOne({ where: { Id: firstAtt.EmailMessageId } });
+          if (emailEntity) {
+            this.imapFolderService.moveToImportiert(emailEntity.MessageId).catch(err =>
+              this.logger.error('IMAP-Verschieben fehlgeschlagen: ' + err.message),
+            );
+          }
         }
       }