feat: migrate Firebase → NestJS REST API backend

Replace all Firebase SDK (Auth, Firestore, Storage) with HTTP calls
to backend.prosapp.co/api/v1:

- New ApiService singleton (JWT token, GET/POST/PATCH/DELETE/upload)
- auth_provider: Firebase Auth → /auth/login, /auth/register, /auth/phone/*
- services_provider + calendar_services_provider → /services endpoints
- professional_provider + professionals_provider → /professional-info, /users/professionals
- profile_form_provider + professional_form_provider → /users/me, /storage/upload
- cities/professions/settings providers → /cities, /professions, /settings
- firebase_chat_repository → polling via /chats endpoints (3s interval)
- firebase_score_repository → polling via /comments endpoints (10s interval)
- professional_detail_provider → /users/:id + /professional-info/:id
- dashboard_view: Firestore.add → POST /services
- chat_view + rating_view: FirebaseAuth.uid → AuthProvider.user.id
- Models: Timestamp → String for createdAt fields
- google_fonts upgraded to ^8.1.0 (Dart 3.12 compat)
- Remove firebase_core, firebase_auth, cloud_firestore, firebase_storage from pubspec

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

lib/providers/professional_provider.dart

@@ -1,32 +1,24 @@
-import 'package:cloud_firestore/cloud_firestore.dart';
-import 'package:firebase_auth/firebase_auth.dart';
 import 'package:flutter/widgets.dart';
 import 'package:prosapp_web_app/models/location_preferences.dart';
 import 'package:prosapp_web_app/models/payment_method_entity.dart';
 import 'package:prosapp_web_app/models/profesional.dart';
 import 'package:prosapp_web_app/models/schedules.dart';
+import 'package:prosapp_web_app/services/api_service.dart';
 
 class ProfessionalProvider extends ChangeNotifier {
   Profesional? profesional;
   bool _isProModeActive = false;
+  final _api = ApiService.instance;
 
-  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
-
-  bool get isProModeActive {
-    return _isProModeActive;
-  }
+  bool get isProModeActive => _isProModeActive;
 
   Future<Profesional> getProfessional(String uid) async {
     try {
-      final professional = await FirebaseFirestore.instance
-          .collection('professional_info')
-          .doc(uid)
-          .get();
-
-      profesional = Profesional.fromDocument(professional.data()!);
+      final data = await _api.get('/professional-info/$uid');
+      profesional = Profesional.fromDocument(data as Map<String, dynamic>);
     } catch (e) {
       profesional = Profesional(
-        id: _firebaseAuth.currentUser!.uid,
+        id: uid,
         identification: '',
         address: '',
         aditionalAddress: '',
@@ -45,12 +37,11 @@ class ProfessionalProvider extends ChangeNotifier {
         paymentMethods: PaymentMethodEntity.empty,
       );
     }
-
     notifyListeners();
     return profesional!;
   }
 
-  logout() {
+  void logout() {
     _isProModeActive = false;
     notifyListeners();
   }