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/models/comment_entity.dart

@@ -1,5 +1,3 @@
-import 'package:cloud_firestore/cloud_firestore.dart';
-
 class CommentEntity {
   final String authorId;
   final String destinationId;
@@ -7,7 +5,7 @@ class CommentEntity {
   final String content;
   final double score;
   final bool isFromUser;
-  final Timestamp createdAt;
+  final String createdAt;
 
   const CommentEntity({
     required this.authorId,
@@ -21,13 +19,13 @@ class CommentEntity {
 
   static CommentEntity fromDocument(Map<String, dynamic> doc) {
     return CommentEntity(
-      authorId: doc['author_id'] as String,
-      destinationId: doc['destination_id'] as String,
-      serviceId: doc['service_id'] as String,
-      content: doc['content'] as String,
-      score: doc['score'] as double,
-      isFromUser: doc['is_from_user'] as bool,
-      createdAt: doc['created_at'] as Timestamp,
+      authorId: doc['author_id'] as String? ?? '',
+      destinationId: doc['destination_id'] as String? ?? '',
+      serviceId: doc['service_id'] as String? ?? '',
+      content: doc['content'] as String? ?? '',
+      score: (doc['score'] as num?)?.toDouble() ?? 0.0,
+      isFromUser: doc['is_from_user'] as bool? ?? false,
+      createdAt: doc['created_at']?.toString() ?? '',
     );
   }
 
@@ -45,14 +43,6 @@ class CommentEntity {
 
   @override
   String toString() {
-    return '''CommentEntity{
-      authorId: $authorId, 
-      destinationId: $destinationId, 
-      serviceId: $serviceId, 
-      content: $content, 
-      score: $score, 
-      isFromUser: $isFromUser, 
-      createdAt: $createdAt
-      }''';
+    return 'CommentEntity{authorId: $authorId, destinationId: $destinationId, score: $score}';
   }
 }