feat: Add services for managing trip-related data

- Implement EmergencyService for handling emergency contacts per trip.
- Create GuestFlagService to manage guest mode flags for trips.
- Introduce NotificationService with local notification capabilities.
- Add OfflineFlagService for managing offline caching flags.
- Develop PackingService for shared packing lists per trip.
- Implement ReminderService for managing reminders/to-dos per trip.
- Create SosService for dispatching SOS events to a backend.
- Add StorageService with album image upload functionality.
- Implement TransportService for managing transport segments per trip.
- Create TripChecklistService for storing and retrieving trip checklists.
- Add TripDocumentService for persisting trip documents metadata.

test: Add unit tests for new services

- Implement tests for AlbumService, BudgetService, EmergencyService, GuestFlagService, PackingService, ReminderService, SosService, TransportService, TripChecklistService, and TripDocumentService.
- Ensure tests cover adding, loading, deleting, and handling corrupted payloads for each service.

lib/services/storage_service.dart

@@ -50,6 +50,43 @@ class StorageService {
     : _storage = storage ?? FirebaseStorage.instance,
       _errorService = errorService ?? ErrorService();
 
+  /// Uploads an album image for a trip with compression.
+  ///
+  /// Saves the file under `album/<tripId>/` with a unique name, and returns
+  /// the download URL. Uses the same compression pipeline as receipts.
+  Future<String> uploadAlbumImage(String tripId, File imageFile) async {
+    try {
+      _validateImageFile(imageFile);
+      final compressedImage = await _compressImage(imageFile);
+      final fileName =
+          'album_${DateTime.now().millisecondsSinceEpoch}_${path.basename(imageFile.path)}';
+      final storageRef = _storage.ref().child('album/$tripId/$fileName');
+
+      final metadata = SettableMetadata(
+        contentType: 'image/jpeg',
+        customMetadata: {
+          'tripId': tripId,
+          'uploadedAt': DateTime.now().toIso8601String(),
+          'compressed': 'true',
+        },
+      );
+
+      final uploadTask = storageRef.putData(compressedImage, metadata);
+
+      final snapshot = await uploadTask;
+      final downloadUrl = await snapshot.ref.getDownloadURL();
+
+      _errorService.logSuccess(
+        'StorageService',
+        'Album image uploaded: $fileName',
+      );
+      return downloadUrl;
+    } catch (e) {
+      _errorService.logError('StorageService', 'Error uploading album image: $e');
+      rethrow;
+    }
+  }
+
   /// Uploads a receipt image for an expense with automatic compression.
   ///
   /// Validates the image file, compresses it to JPEG format with 85% quality,