feat: Flutter 客户端 App + Web UI APK 下载入口

- 新增 Flutter 跨平台客户端项目 (clients/flutter/)
  - 29 个 Dart 文件: 服务层/状态管理/5个页面/BLE配网
  - BLE 蓝牙配网: 扫描设备、写入WiFi凭据、配网状态监听
  - HTTP API 客户端: 覆盖全部端点 (播放/场景/WiFi/视频/配置/文件/插件)
  - WebSocket 实时通信: 事件流 + 自动重连
  - 暗色主题 Material 3 UI, 中文界面
  - Android 配置: minSdkVersion 21, BLE/网络权限
  - PRD 产品需求文档 + 开发任务看板
- Web UI 添加 APK 下载入口 (routes.rs)
  - 下载弹窗 + 二维码 + /download/{filename} 静态文件路由
- BLE 插件增加自动重连循环 (ble/mod.rs)
- BLE 默认设备名修正为 'Showen' (config.rs)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

clients/flutter/lib/providers/player_provider.dart

@@ -0,0 +1,184 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+
+import '../models/player_status.dart';
+import '../services/http_api_service.dart';
+import '../services/web_socket_service.dart';
+
+class PlayerProvider extends ChangeNotifier {
+  PlayerProvider({
+    required HttpApiService httpApiService,
+    required WebSocketService webSocketService,
+  })  : _httpApiService = httpApiService,
+        _webSocketService = webSocketService {
+    _statusSubscription = _webSocketService.onStatusUpdate.listen((payload) {
+      _status = PlayerStatus.fromJson(payload);
+      notifyListeners();
+    });
+    _stateSubscription = _webSocketService.onStateUpdate.listen((payload) {
+      _currentState = payload['new_state']?.toString() ?? _currentState;
+      notifyListeners();
+    });
+    _configSubscription = _webSocketService.onConfigUpdate.listen((payload) {
+      _updateSceneOptions(payload);
+      notifyListeners();
+    });
+  }
+
+  final HttpApiService _httpApiService;
+  final WebSocketService _webSocketService;
+  late final StreamSubscription<Map<String, dynamic>> _statusSubscription;
+  late final StreamSubscription<Map<String, dynamic>> _stateSubscription;
+  late final StreamSubscription<Map<String, dynamic>> _configSubscription;
+
+  PlayerStatus _status = PlayerStatus.initial();
+  List<String> _playlist = const <String>[];
+  List<String> _sceneOptions = const <String>['idle', 'intro', 'loop'];
+  bool _isLoading = false;
+  String? _errorMessage;
+  String? _currentState;
+
+  PlayerStatus get status => _status;
+  List<String> get playlist => _playlist;
+  List<String> get sceneOptions => _sceneOptions;
+  bool get isLoading => _isLoading;
+  String? get errorMessage => _errorMessage;
+  String get currentState => _currentState ?? _status.currentVideo ?? 'idle';
+
+  Future<void> bootstrap() async {
+    _setLoading(true);
+    try {
+      final results = await Future.wait<dynamic>([
+        _httpApiService.getPlaybackStatus(),
+        _httpApiService.getPlaylist(),
+        _httpApiService.getConfig(),
+      ]);
+      _status = results[0] as PlayerStatus;
+      _playlist = results[1] as List<String>;
+      _updateSceneOptions(results[2] as Map<String, dynamic>);
+      _errorMessage = null;
+    } catch (error) {
+      _errorMessage = error.toString();
+    } finally {
+      _setLoading(false);
+    }
+  }
+
+  Future<void> fetchStatus() async {
+    try {
+      _status = await _httpApiService.getPlaybackStatus();
+      _errorMessage = null;
+      notifyListeners();
+    } catch (error) {
+      _errorMessage = error.toString();
+      notifyListeners();
+    }
+  }
+
+  Future<void> fetchPlaylist() async {
+    try {
+      _playlist = await _httpApiService.getPlaylist();
+      _errorMessage = null;
+      notifyListeners();
+    } catch (error) {
+      _errorMessage = error.toString();
+      notifyListeners();
+    }
+  }
+
+  Future<void> play() => _runCommand(_httpApiService.play);
+
+  Future<void> pause() => _runCommand(_httpApiService.pause);
+
+  Future<void> next() => _runCommand(_httpApiService.next);
+
+  Future<void> previous() => _runCommand(_httpApiService.previous);
+
+  Future<void> gotoIndex(int index) async {
+    await _runCommand(() => _httpApiService.goto(index));
+  }
+
+  Future<void> switchScene(String name) async {
+    await _runCommand(() => _httpApiService.changeScene(name));
+    _currentState = name;
+    notifyListeners();
+  }
+
+  Future<void> triggerEvent(String name, {String? value}) {
+    return _runCommand(() => _httpApiService.trigger(name, value));
+  }
+
+  Future<void> togglePlayPause() async {
+    if (_status.running && !_status.paused) {
+      await pause();
+      return;
+    }
+    await play();
+  }
+
+  Future<void> _runCommand(Future<dynamic> Function() action) async {
+    _setLoading(true);
+    try {
+      await action();
+      await Future.wait<void>([
+        fetchStatus(),
+        fetchPlaylist(),
+      ]);
+      _errorMessage = null;
+    } catch (error) {
+      _errorMessage = error.toString();
+      notifyListeners();
+    } finally {
+      _setLoading(false);
+    }
+  }
+
+  void _updateSceneOptions(Map<String, dynamic> config) {
+    final candidates = <String>{};
+    final scenes = config['scenes'];
+    if (scenes is List) {
+      for (final scene in scenes) {
+        final value = scene.toString();
+        if (value.isNotEmpty) {
+          candidates.add(value);
+        }
+      }
+    }
+
+    final stateMachine = config['state_machine'];
+    if (stateMachine is Map) {
+      final states = stateMachine['states'];
+      if (states is Map) {
+        for (final entry in states.keys) {
+          final value = entry.toString();
+          if (value.isNotEmpty) {
+            candidates.add(value);
+          }
+        }
+      }
+      final initialState = stateMachine['initial_state']?.toString();
+      if (initialState != null && initialState.isNotEmpty) {
+        candidates.add(initialState);
+        _currentState ??= initialState;
+      }
+    }
+
+    if (candidates.isNotEmpty) {
+      _sceneOptions = candidates.toList(growable: false)..sort();
+    }
+  }
+
+  void _setLoading(bool value) {
+    _isLoading = value;
+    notifyListeners();
+  }
+
+  @override
+  void dispose() {
+    unawaited(_statusSubscription.cancel());
+    unawaited(_stateSubscription.cancel());
+    unawaited(_configSubscription.cancel());
+    super.dispose();
+  }
+}