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>

packages/chat_repository/lib/chat_repository.dart

@@ -2,3 +2,4 @@ library chat_repository;
 
 export 'src/entities/entities.dart';
 export 'src/repositories/firebase_chat_repository.dart';
+export 'src/repositories/api_chat_repository.dart';

packages/chat_repository/lib/src/repositories/api_chat_repository.dart

@@ -0,0 +1,121 @@
+import 'dart:async';
+import 'dart:convert';
+import 'package:http/http.dart' as http;
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:chat_repository/chat_repository.dart';
+
+const _base = 'https://backend.prosapp.co/api/v1';
+
+/// API-backed replacement for FirebaseChatRepository.
+/// Mirrors the same public API so existing blocs work without changes.
+class ApiChatRepository {
+  String? _token;
+
+  Future<String?> _getToken() async {
+    if (_token != null) return _token;
+    final prefs = await SharedPreferences.getInstance();
+    return _token = prefs.getString('token');
+  }
+
+  Future<Map<String, String>> _headers() async {
+    final t = await _getToken();
+    return {
+      'Content-Type': 'application/json',
+      if (t != null) 'Authorization': 'Bearer $t',
+    };
+  }
+
+  ChatEntity _chatFromApi(Map<String, dynamic> json) {
+    final rawMessages = json['messages'] as List? ?? [];
+    final messages = rawMessages
+        .map((m) => MessageEntity.fromDocument(m as Map<String, dynamic>))
+        .toList();
+    return ChatEntity(
+      id: json['id']?.toString(),
+      userId: json['user_id']?.toString() ?? json['userId']?.toString() ?? '',
+      professionalId: json['professional_id']?.toString() ??
+          json['professionalId']?.toString() ??
+          '',
+      messages: messages,
+    );
+  }
+
+  MessageEntity _msgFromApi(Map<String, dynamic> json) {
+    return MessageEntity(
+      ownerId: json['owner_id']?.toString() ?? json['sender_id']?.toString() ?? '',
+      content: json['content']?.toString() ?? '',
+      createdAt: json['created_at'] != null
+          ? DateTime.tryParse(json['created_at'].toString()) ?? DateTime.now()
+          : DateTime.now(),
+    );
+  }
+
+  /// Get or create a chat session. Maps to POST /chat/start/:professionalUserId.
+  /// [chatId] here is used as the professional's userId for the REST call.
+  Future<ChatEntity> createNewChat(
+      String chatId, String userId, String professionalId) async {
+    final res = await http.post(
+      Uri.parse('$_base/chat/start/$professionalId'),
+      headers: await _headers(),
+    );
+    final data = jsonDecode(res.body) as Map<String, dynamic>;
+    return _chatFromApi(data);
+  }
+
+  /// Streams a single chat by its ID. Fetches once and emits.
+  Stream<ChatEntity?> getChatById(String chatId) {
+    final controller = StreamController<ChatEntity?>();
+    _fetchChat(chatId).then((chat) {
+      controller.add(chat);
+      controller.close();
+    }).catchError((e) {
+      controller.add(null);
+      controller.close();
+    });
+    return controller.stream;
+  }
+
+  Future<ChatEntity?> _fetchChat(String chatId) async {
+    try {
+      // Try to get messages for this chat — if the chat exists it'll succeed
+      final res = await http.get(
+        Uri.parse('$_base/chat/$chatId/messages'),
+        headers: await _headers(),
+      );
+      if (res.statusCode == 404) return null;
+      final messages = jsonDecode(res.body) as List? ?? [];
+      return ChatEntity(
+        id: chatId,
+        userId: '',
+        professionalId: '',
+        messages: messages
+            .map((m) => _msgFromApi(m as Map<String, dynamic>))
+            .toList(),
+      );
+    } catch (_) {
+      return null;
+    }
+  }
+
+  Future<void> sendMessage(String chatId, MessageEntity message) async {
+    await http.post(
+      Uri.parse('$_base/chat/$chatId/message'),
+      headers: await _headers(),
+      body: jsonEncode({'content': message.content}),
+    );
+  }
+
+  /// Get all chats for the current user.
+  Future<List<ChatEntity>> getMyChats() async {
+    try {
+      final res = await http.get(
+        Uri.parse('$_base/chat/my'),
+        headers: await _headers(),
+      );
+      final data = jsonDecode(res.body) as List? ?? [];
+      return data.map((e) => _chatFromApi(e as Map<String, dynamic>)).toList();
+    } catch (_) {
+      return [];
+    }
+  }
+}

packages/chat_repository/pubspec.yaml

@@ -11,8 +11,10 @@ dependencies:
   flutter:
     sdk: flutter
   equatable: ^2.0.5
+  http: ^1.1.0
+  shared_preferences: ^2.0.10
 
-  # Firebase
+  # Firebase kept for FirebaseChatRepository (legacy fallback)
   cloud_firestore: ^4.15.4
   firebase_core: ^2.25.4
 
@@ -22,4 +24,4 @@ dev_dependencies:
     sdk: flutter
 
 flutter:
-  uses-material-design: true
+  uses-material-design: true