feat: 实现会话配置与多轮上下文

- 新增 ConfigPanel 组件：TTS 开关、detail level、语言选择
- 新增 storage.ts：配置持久化到 localStorage
- useVisionSession：连接后自动发送 config，维护最近 10 轮对话历史
- App：齿轮按钮展开配置面板，HD 角标，TTS 播放联动 ttsEnabled

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

frontend/src/App.tsx

@@ -2,13 +2,17 @@
 // CamTalk — 主应用组件
 // ============================================================
 
+import { useState } from "react";
 import { useVisionSession } from "./hooks/useVisionSession";
 import { VideoPreview } from "./components/VideoPreview";
 import { ChatPanel } from "./components/ChatPanel";
+import { ConfigPanel } from "./components/ConfigPanel";
 import { ToastContainer } from "./components/Toast";
 import "./App.css";
 
 function App() {
+  const [showConfig, setShowConfig] = useState(false);
+
   const {
     messages,
     currentReply,
@@ -20,6 +24,8 @@ function App() {
     connectionStatus,
     videoRef,
     stream,
+    config,
+    updateConfig,
     startSession,
     stopSession,
     interrupt,
@@ -31,20 +37,44 @@ function App() {
     <div className="app">
       <header className="app-header">
         <h1>CamTalk</h1>
-        <span className={`status status--${connectionStatus}`}>
-          {isConnected
-            ? "已连接"
-            : connectionStatus === "connecting"
-              ? "连接中..."
-              : "未连接"}
-        </span>
+        <div className="header-right">
+          <span className={`status status--${connectionStatus}`}>
+            {isConnected
+              ? "已连接"
+              : connectionStatus === "connecting"
+                ? "连接中..."
+                : "未连接"}
+          </span>
+          {isConnected && (
+            <button
+              className="btn-icon"
+              onClick={() => setShowConfig((v) => !v)}
+              title="设置"
+            >
+              ⚙️
+            </button>
+          )}
+        </div>
       </header>
 
+      {showConfig && (
+        <ConfigPanel
+          config={config}
+          onUpdate={updateConfig}
+          onClose={() => setShowConfig(false)}
+        />
+      )}
+
       <main className="app-main">
         <div className="video-section">
           <VideoPreview ref={videoRef} isStreaming={!!stream} />
+          {config.detailLevel === "high" && (
+            <div className="detail-badge">HD</div>
+          )}
           {isSpeaking && <div className="vad-indicator">🎤 正在聆听...</div>}
-          {isAudioPlaying && <div className="vad-indicator vad-indicator--audio">🔊 正在播放...</div>}
+          {isAudioPlaying && config.ttsEnabled && (
+            <div className="vad-indicator vad-indicator--audio">🔊 正在播放...</div>
+          )}
           {isConnected && !isVADReady && !vadError && (
             <div className="vad-indicator vad-indicator--loading">
               正在初始化语音检测...