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/screens/professional/professional_calendar_screen.dart

@@ -1,4 +1,3 @@
-import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
@@ -28,7 +27,7 @@ class ProfessionalCalendarScreen extends StatefulWidget {
 class _ProfessionalCalendarScreenState extends State<ProfessionalCalendarScreen> {
   final settingRepository = Injector.appInstance.get<SettingRepository>();
   final serviceRepository =
-      Injector.appInstance.get<FirebaseServiceRepository>();
+      Injector.appInstance.get<ApiServiceRepository>();
   SettingEntity? settings;
 
   DateTime today = DateTime.now();
@@ -352,7 +351,7 @@ class _ProfessionalCalendarScreenState extends State<ProfessionalCalendarScreen>
                                   latitude: 0,
                                   longitude: 0,
                                   day: today.toString(),
-                                  createdAt: Timestamp.now(),
+                                  createdAt: DateTime.now().toIso8601String(),
                                   description: '',
                                   range1Hour1: time,
                                   range1Hour2: time.add(hour: 2),