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/profession_repository/lib/profession_repository.dart

@@ -3,4 +3,5 @@ library profession_repository;
 export 'src/models/models.dart';
 export 'src/entities/entities.dart';
 export 'src/repositories/profession_repo.dart';
-export 'src/repositories/firebase_profession_repository.dart';
+export 'src/repositories/firebase_profession_repository.dart';
+export 'src/repositories/api_profession_repository.dart';

packages/profession_repository/lib/src/repositories/api_profession_repository.dart

@@ -0,0 +1,46 @@
+import 'dart:async';
+import 'dart:convert';
+import 'package:http/http.dart' as http;
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:profession_repository/profession_repository.dart';
+import 'profession_repo.dart';
+
+const _base = 'https://backend.prosapp.co/api/v1';
+
+class ApiProfessionRepository implements ProfessionRepository {
+  Future<String?> _getToken() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getString('token');
+  }
+
+  Future<Map<String, String>> _headers() async {
+    final t = await _getToken();
+    return {
+      'Content-Type': 'application/json',
+      if (t != null) 'Authorization': 'Bearer $t',
+    };
+  }
+
+  @override
+  Future<Professions> getProfessions() async {
+    try {
+      final res = await http.get(
+        Uri.parse('$_base/professions'),
+        headers: await _headers(),
+      );
+      final data = jsonDecode(res.body);
+      // Backend returns either a list of profession objects or a map with a professions key
+      if (data is List) {
+        final names = data
+            .map((e) => (e['name'] ?? e['title'] ?? e.toString()).toString())
+            .toList();
+        return Professions(names);
+      } else if (data is Map && data.containsKey('professions')) {
+        return Professions(List<String>.from(data['professions']));
+      }
+      return Professions([]);
+    } catch (e) {
+      rethrow;
+    }
+  }
+}