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/professionals_provider.dart

@@ -1,14 +1,11 @@
-import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:flutter/material.dart';
-import 'package:prosapp_web_app/models/comment_entity.dart';
-import 'package:prosapp_web_app/models/pro_state.dart';
-import 'package:prosapp_web_app/models/profesional.dart';
-import 'package:prosapp_web_app/models/usuario.dart';
 import 'package:prosapp_web_app/models/usuario_profesional.dart';
+import 'package:prosapp_web_app/services/api_service.dart';
 
 class ProfessionalsProvider extends ChangeNotifier {
   List<UsuarioProfesional> professionals = [];
   bool isLoading = true;
+  final _api = ApiService.instance;
 
   ProfessionalsProvider() {
     getProfessionals();
@@ -16,42 +13,10 @@ class ProfessionalsProvider extends ChangeNotifier {
 
   getProfessionals() async {
     try {
-      final querySnapshot = await FirebaseFirestore.instance
-          .collection('users')
-          .where('professional_state', isEqualTo: ProState.active.index)
-          .get();
-
-      final users = querySnapshot.docs
-          .map((e) => Usuario.fromDocument(e.data()))
+      final data = await _api.get('/users/professionals');
+      professionals = (data as List)
+          .map((e) => UsuarioProfesional.fromDocument(e as Map<String, dynamic>))
           .toList();
-
-      final ids = users.map((e) => e.id).toList();
-
-      final querySnapshot2 = await FirebaseFirestore.instance
-          .collection('professional_info')
-          .where(FieldPath.documentId, whereIn: ids)
-          .get();
-
-      final professionalsInfo = querySnapshot2.docs
-          .map((e) => Profesional.fromDocument(e.data()))
-          .toList();
-
-      final professionalInfoMap = {
-        for (var doc in professionalsInfo) doc.id: doc
-      };
-
-      final usersMap = await Future.wait(users.map((user) async {
-        final professionalInfo = professionalInfoMap[user.id];
-        final averageScore = await _getAverageScore(user.id);
-        return UsuarioProfesional(
-          user: user,
-          professionalInfo: professionalInfo!,
-          averageScore: averageScore,
-        );
-      }).toList());
-
-      professionals = usersMap;
-
     } catch (e) {
       print('Error obteniendo profesionales: $e');
     } finally {
@@ -59,22 +24,4 @@ class ProfessionalsProvider extends ChangeNotifier {
       notifyListeners();
     }
   }
-
-  Future<double> _getAverageScore(String userId) async {
-    final querySnapshot = await FirebaseFirestore.instance
-        .collection('comments')
-        .where('destination_id', isEqualTo: userId)
-        .where('is_from_user', isEqualTo: true)
-        .get();
-
-    if (querySnapshot.docs.isEmpty) {
-      return 0.0;
-    }
-
-    final scores = querySnapshot.docs
-        .map((e) => CommentEntity.fromDocument(e.data()).score)
-        .toList();
-    final averageScore = scores.reduce((a, b) => a + b) / scores.length;
-    return averageScore;
-  }
 }