fix: 修复安卓 Chrome 无音频问题，移除强制 16kHz 采样率，添加 AudioContext resume

web/app.js

@@ -173,9 +173,12 @@
   // ── Audio pipeline ──
   async function initAudio() {
     if (state.audioCtx) return;
-    const audioCtx = new (window.AudioContext || window.webkitAudioContext)({
-      sampleRate: TARGET_SAMPLE_RATE, // Request 16kHz directly (Chrome supports)
-    });
+    // Use device native sample rate — we resample to 16kHz in software
+    const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
+    // Chrome requires resume() after user gesture
+    if (audioCtx.state === "suspended") {
+      await audioCtx.resume();
+    }
     await audioCtx.audioWorklet.addModule("audio-processor.js");
     state.audioCtx = audioCtx;
   }
@@ -183,6 +186,10 @@
     if (state.recording) return;
     try {
       await initAudio();
+      // Ensure AudioContext is running (may suspend between recordings)
+      if (state.audioCtx.state === "suspended") {
+        await state.audioCtx.resume();
+      }
       const stream = await navigator.mediaDevices.getUserMedia({
         audio: { echoCancellation: true, noiseSuppression: true, channelCount: 1 },
       });