feat(05-04): add WebSocket play/pause messages to wireAudio() event listeners

- audio 'play' listener now sends client.send({ type: 'play', position }) to server
- audio 'pause' listener now sends client.send({ type: 'pause', position }) to server
- Server is_playing flag now set correctly on mouse-initiated playback
- UDP cue scheduler fires for both mouse and keyboard playback

lightsync/frontend/app.js

@@ -132,8 +132,8 @@ function wireAudio() {
         else audio.pause();
     });
 
-    audio.addEventListener('play',  () => { btn.textContent = '⏸'; startTicks(); });
-    audio.addEventListener('pause', () => { btn.textContent = '▶'; stopTicks(); });
+    audio.addEventListener('play',  () => { btn.textContent = '⏸'; startTicks(); client.send({ type: 'play', position: audio.currentTime }); });
+    audio.addEventListener('pause', () => { btn.textContent = '▶'; stopTicks(); client.send({ type: 'pause', position: audio.currentTime }); });
     audio.addEventListener('ended', () => { btn.textContent = '▶'; stopTicks(); seek.value = 0; });
 
     // Time display + seek bar sync