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/cities_provider.dart

@@ -1,49 +1,35 @@
 import 'package:flutter/material.dart';
-import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:prosapp_web_app/models/city.dart';
-import 'package:prosapp_web_app/models/country_entity.dart';
+import 'package:prosapp_web_app/services/api_service.dart';
 
 class CitiesProvider extends ChangeNotifier {
   List<City> cities = [];
   bool isLoading = true;
-
-  final _citiesCollection =
-      FirebaseFirestore.instance.collection('countries v2');
+  final _api = ApiService.instance;
 
   CitiesProvider() {
     getCities();
   }
 
   getCoordsOfCity(String cityName) {
-    if (cities.isEmpty) return null;
-
     for (var city in cities) {
-      if (city.cityName == cityName) {
-        return city.coordsOfCity;
-      }
+      if (city.cityName == cityName) return city.coordsOfCity;
     }
     return null;
   }
 
   getCities() async {
     try {
-      final querySnapshot = await _citiesCollection.doc('Colombia').get();
-
-      final data = querySnapshot.data();
-
-      final country = CountryEntity.fromDocument(data as Map<String, dynamic>);
-
-      for (var region in country.regions) {
-        for (var city in region.cities) {
-          cities.add(City(
-            cityName: city.name,
-            coordsOfCity: city.coords,
-            stateOfCity: region.name,
-            countryOfCity: country.name,
-          ));
-        }
-      }
-
+      final data = await _api.get('/cities') as List;
+      cities = data.map((e) {
+        final m = e as Map<String, dynamic>;
+        return City(
+          cityName: m['name'] as String,
+          coordsOfCity: m['coords'] as String? ?? '',
+          stateOfCity: m['state'] as String? ?? '',
+          countryOfCity: m['country'] as String? ?? 'Colombia',
+        );
+      }).toList();
       cities.sort((a, b) => a.cityName.compareTo(b.cityName));
     } catch (e) {
       print('Error obteniendo ciudades: $e');