feat: migrate prosappco from Firebase to NestJS REST API (Fase 2)

- Replace all Firebase* repositories with Api* repositories using HTTP + SharedPreferences JWT
- Remove Firebase.initializeApp() and firebase_messaging background handler from main.dart
- Update DI (app_di.dart) to inject Api* repositories instead of Firebase* ones
- Replace all Timestamp/cloud_firestore usage with ISO 8601 String dates
- Stub PhoneVerificationService (Firebase phone OTP → backend OTP when implemented)
- Add ApiService singleton with JWT management in lib/services/
- Legacy firebase_*_repository.dart files preserved for Fase 4 cleanup

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

lib/blocs/notification_bloc/notification_state.dart

@@ -1,5 +1,13 @@
 part of 'notification_bloc.dart';
 
+// Stub for firebase_messaging AuthorizationStatus
+enum AuthorizationStatus {
+  authorized,
+  denied,
+  notDetermined,
+  provisional,
+}
+
 class NotificationState extends Equatable {
   final AuthorizationStatus status;