chore: apply ESLint auto-fix across entire backend

Reformats code style (line breaks, indentation, type annotations)
without changing logic. Also includes minor feature additions bundled
in the same lint run (stats service, user-settings groups, agrarmonitor
polling improvements).

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

paperless-backend/src/database/entities/postprocessing.entity.ts

@@ -1,7 +1,7 @@
 import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';
 
 export interface FilterCondition {
-  field: string;    // 'document_type' | 'correspondent' | 'owner' | 'tag' | 'custom_field_<id>' | 'title' | 'archive_serial_number'
+  field: string; // 'document_type' | 'correspondent' | 'owner' | 'tag' | 'custom_field_<id>' | 'title' | 'archive_serial_number'
   operator: string; // 'equals' | 'not_equals' | 'contains' | 'not_contains' | 'is_set' | 'is_not_set'
   value: any;
 }