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/auth/jwt.strategy.ts

@@ -24,7 +24,14 @@ export class JwtStrategy extends PassportStrategy(Strategy, 'jwt') {
     });
   }
 
-  validate(payload: any): { userId: string; email: string; name: string; preferredUsername: string | null; groups: string[]; permissions: any[] } {
+  validate(payload: any): {
+    userId: string;
+    email: string;
+    name: string;
+    preferredUsername: string | null;
+    groups: string[];
+    permissions: any[];
+  } {
     const groups = payload.groups || [];
     return {
       userId: payload.sub,