Initial commit: Captain Claude Mobile App

- Flutter app with chat and terminal screens
- WebSocket integration for real-time chat
- xterm integration for screen sessions
- Markdown rendering with code blocks
- JWT authentication

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/services/auth_service.dart

@@ -0,0 +1,61 @@
+import 'dart:convert';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import '../models/user.dart';
+import 'api_service.dart';
+
+class AuthService {
+  final ApiService _apiService;
+  final FlutterSecureStorage _storage = const FlutterSecureStorage();
+
+  static const String _userKey = 'captain_user';
+
+  AuthService(this._apiService);
+
+  Future<User?> login(String username, String password) async {
+    try {
+      final response = await _apiService.login(username, password);
+      final user = User(
+        username: username,
+        token: response['token'],
+        expiresAt: DateTime.parse(response['expires_at']),
+      );
+
+      await _saveUser(user);
+      _apiService.setToken(user.token);
+
+      return user;
+    } catch (e) {
+      return null;
+    }
+  }
+
+  Future<User?> getStoredUser() async {
+    try {
+      final data = await _storage.read(key: _userKey);
+      if (data == null) return null;
+
+      final user = User.fromJson(jsonDecode(data));
+      if (user.isExpired) {
+        await logout();
+        return null;
+      }
+
+      _apiService.setToken(user.token);
+      return user;
+    } catch (e) {
+      return null;
+    }
+  }
+
+  Future<void> _saveUser(User user) async {
+    await _storage.write(
+      key: _userKey,
+      value: jsonEncode(user.toJson()),
+    );
+  }
+
+  Future<void> logout() async {
+    await _storage.delete(key: _userKey);
+    _apiService.setToken(null);
+  }
+}