fix(voice): add clear error message for HTTP mediaDevices restriction

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/composables/useVoiceRoom.ts

@@ -32,6 +32,11 @@ export function useVoiceRoom() {
   async function connect(sessionId: string) {
     try {
       error.value = null
+
+      if (!navigator.mediaDevices?.getUserMedia) {
+        throw new Error('浏览器不允许在 HTTP 下使用麦克风。请在 Chrome 地址栏输入 chrome://flags/#unsafely-treat-insecure-origin-as-secure，启用后将 http://192.168.1.14:7033 加入白名单，然后重启浏览器。')
+      }
+
       const token = await fetchVoiceToken(sessionId)
       const livekitUrl = getLiveKitUrl()