fix: disable auto-retry and improve error messages in Agrarmonitor

- Set autoRetry: false and timeoutMs: 10000 in AgrarmonitorService
- Show specific error message on timeout or backend error in frontend

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

paperless-backend/src/agrarmonitor/agrarmonitor.service.ts

@@ -48,7 +48,8 @@ export class AgrarmonitorService {
       password,
       cookieStore,
       autoLogin: true,
-      autoRetry: true,
+      autoRetry: false,
+      timeoutMs: 10000,
       logger: this.logger,
     });