fix: edge case bugs + toggle lyrics from player bar and lyrics button

Bugs fixed:
- play-at: stop current playback before jumping to queue index
- playNext retry: use break instead of return to ensure stateChange emits
- sendVoiceData: skip if disconnecting to avoid errors during teardown

UI: player-left and lyrics button now toggle lyrics page (open/close)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ts-protocol/client.ts

@@ -154,8 +154,7 @@ export class TS3Client extends EventEmitter {
   }
 
   sendVoiceData(opusFrame: Buffer): void {
-    if (!this.client) return;
-    // Codec 5 = CODEC_OPUS_MUSIC
+    if (!this.client || this.disconnecting) return;
     this.client.sendVoice(opusFrame, 5);
   }