Phase 1 scaffold: auth for all apps

- Backend: Fastify with two listeners (public + internal), routes, services, DB migration + seed
- client_app: Flutter with BLoC, all auth screens (welcome, display name, register, OTP, force-register)
- mitra_app: Flutter with BLoC, OTP-only login
- control_center: React + Vite, email/password login, mitra/user management, anonymity settings
- Docs: phase1 plan, API contract, client app mockup
- CLAUDE.md and shared memory for all subprojects

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mitra_app/lib/core/api/api_client.dart

@@ -0,0 +1,30 @@
+import 'package:dio/dio.dart';
+import 'package:firebase_auth/firebase_auth.dart';
+
+class ApiClient {
+  static const String _baseUrl = String.fromEnvironment(
+    'API_BASE_URL',
+    defaultValue: 'https://api.halobestie.com',
+  );
+
+  late final Dio _dio;
+
+  ApiClient() {
+    _dio = Dio(BaseOptions(baseUrl: _baseUrl));
+    _dio.interceptors.add(InterceptorsWrapper(
+      onRequest: (options, handler) async {
+        final user = FirebaseAuth.instance.currentUser;
+        if (user != null) {
+          final token = await user.getIdToken();
+          options.headers['Authorization'] = 'Bearer $token';
+        }
+        handler.next(options);
+      },
+    ));
+  }
+
+  Future<Map<String, dynamic>> post(String path, {Map<String, dynamic>? data}) async {
+    final response = await _dio.post(path, data: data);
+    return response.data as Map<String, dynamic>;
+  }
+}