feat: 初始化前端项目，搭建 React + TypeScript + Vite 工程结构

- 创建 Vite + React 18 + TypeScript 项目（严格模式）
- 安装 @ricky0123/vad-web、onnxruntime-web、uuid 依赖
- 定义全部 WebSocket 消息类型和数据模型（对齐接口文档）
- 实现 WebSocket 连接管理（心跳保活、指数退避重连）
- 实现音频编码工具（PCM↔Base64、DataURL 转换）
- 创建组件骨架：CameraManager、MicManager、EdgeProcessor、WebSocketManager、ChatPanel、VideoPreview
- 实现核心 useVisionSession Hook 骨架
- 配置 ESLint（_前缀变量忽略规则）

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

frontend/src/components/WebSocketManager/index.tsx

@@ -0,0 +1,32 @@
+// ============================================================
+// WebSocketManager — WebSocket 连接生命周期管理
+// 职责：管理连接状态、消息分发
+// ============================================================
+
+import { useEffect, useState } from "react";
+import { wsClient } from "../../lib/websocket";
+import type { ConnectionStatus } from "../../lib/websocket";
+import type { ServerMessage } from "../../types";
+
+export function useWebSocketManager() {
+  const [status, setStatus] = useState<ConnectionStatus>(wsClient.status);
+  const [lastMessage, setLastMessage] = useState<ServerMessage | null>(null);
+
+  useEffect(() => {
+    const unsubStatus = wsClient.onStatusChange(setStatus);
+    const unsubMessage = wsClient.onMessage(setLastMessage);
+
+    return () => {
+      unsubStatus();
+      unsubMessage();
+    };
+  }, []);
+
+  return {
+    status,
+    lastMessage,
+    connect: () => wsClient.connect(),
+    disconnect: () => wsClient.disconnect(),
+    send: wsClient.send.bind(wsClient),
+  };
+}