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/service/service_screen.dart

@@ -1,6 +1,5 @@
 import 'dart:async';
 
-import 'package:firebase_auth/firebase_auth.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
@@ -484,16 +483,15 @@ class _ServiceScreenState extends State<ServiceScreen> {
 
   Future<List<dynamic>> _getUserAndProfessionalInfo(
       ServiceEntity service) async {
-    final userRepo = FirebaseUserRepository(FirebaseAuth.instance);
-    final professionalRepo = FirebaseProfessionalRepository();
-    if (FirebaseAuth.instance.currentUser!.uid == service.professionalId) {
+    final userRepo = Injector.appInstance.get<UserRepository>();
+    final professionalRepo = Injector.appInstance.get<ApiProfessionalRepository>();
+    if ((ApiUserRepository.currentUserId ?? '') == service.professionalId) {
       final userInfo = await userRepo.getMyUser(service.userId);
       final professionalInfo =
           await professionalRepo.getProInfo(service.professionalId);
 
       return [userInfo, professionalInfo];
     } else {
-      final userRepo = FirebaseUserRepository(FirebaseAuth.instance);
       final userInfo = await userRepo.getMyUser(service.professionalId);
 
       final professionalInfo =