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/main.ts

@@ -7,7 +7,9 @@ async function bootstrap(): Promise<void> {
   const port = process.env.PORT ?? 3100;
 
   app.enableCors({
-    origin: process.env.CORS_ORIGIN ?? (process.env.NODE_ENV === 'production' ? false : '*'),
+    origin:
+      process.env.CORS_ORIGIN ??
+      (process.env.NODE_ENV === 'production' ? false : '*'),
     methods: 'GET,HEAD,PUT,PATCH,POST,DELETE,OPTIONS',
     credentials: true,
   });