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/main.dart

@@ -1,6 +1,4 @@
-import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/material.dart';
-import 'package:firebase_core/firebase_core.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:injector/injector.dart';
@@ -14,19 +12,13 @@ import 'package:prosappco/blocs/profile_bloc/profile_bloc.dart';
 import 'package:prosappco/dependency/app_di.dart';
 import 'package:prosappco/local_notifications/local_notifications.dart';
 import 'simple_bloc_observer.dart';
-import 'firebase_options.dart';
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
-  await Firebase.initializeApp(
-    options: DefaultFirebaseOptions.currentPlatform,
-  ); // Asegúrate de inicializar Firebase antes de cualquier otra operación relacionada con Firebase.
 
-  // Inicialización de notificaciones locales después de Firebase.
+  // Inicializacion de notificaciones locales
   await LocalNotifications.initializeLocalNotifications();
 
-  FirebaseMessaging.onBackgroundMessage(firebaseMessagingBackgroundHandler);
-
   Bloc.observer = SimpleBlocObserver();
   SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
   AppDI().register();