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>

packages/professional_repository/pubspec.yaml

@@ -11,12 +11,14 @@ dependencies:
   flutter:
     sdk: flutter
   equatable: ^2.0.5
+  http: ^1.1.0
+  shared_preferences: ^2.0.10
+  intl: ^0.19.0
 
-  # Firebase
+  # Firebase kept for FirebaseProfessionalRepository (legacy fallback)
   cloud_firestore: ^4.15.4
   firebase_storage: ^11.6.5
   firebase_core: ^2.25.4
-  intl: ^0.19.0
   firebase_auth: ^4.17.8
 
 dev_dependencies:
@@ -25,4 +27,4 @@ dev_dependencies:
     sdk: flutter
 
 flutter:
-  uses-material-design: true
+  uses-material-design: true