Allow up to 2GB backup restore uploads and 2-hour transfer timeout

backend/src/routes/backup.js

@@ -11,9 +11,10 @@ if (!fs.existsSync(tempUploadsDir)) {
     fs.mkdirSync(tempUploadsDir, { recursive: true });
 }
 
+const maxBackupSizeMB = parseInt(process.env.MAX_BACKUP_SIZE_MB || '2048', 10);
 const upload = multer({
     dest: tempUploadsDir,
-    limits: { fileSize: 500 * 1024 * 1024 } // allow up to 500 MB backup zip files
+    limits: { fileSize: maxBackupSizeMB * 1024 * 1024 } // allow up to 2 GB (2048 MB) by default
 });
 
 router.get('/info', authenticateToken, authorizeRoles('admin', 'superadmin'), backupController.getBackupInfo);

frontend/lib/domain/repositories/backup_repository.dart

@@ -7,8 +7,8 @@ class BackupRepository {
   final Dio _dio = ApiConstants.createDio(
     BaseOptions(
       connectTimeout: const Duration(minutes: 5),
-      sendTimeout: const Duration(minutes: 30), // Long uploads over VPS WAN
-      receiveTimeout: const Duration(minutes: 30), // Zipping & unzipping might take time
+      sendTimeout: const Duration(hours: 2), // Allow up to 2 hours for multi-gigabyte uploads over WAN
+      receiveTimeout: const Duration(hours: 2), // Allow up to 2 hours for extracting large zips
     ),
   );
   final FlutterSecureStorage _storage = const FlutterSecureStorage();