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/web/api/player.ts

@@ -152,6 +152,7 @@ export function createPlayerRouter(
         return;
       }
       const queue = bot.getQueueManager();
+      bot.getPlayer().stop(); // Stop current playback first
       const song = queue.playAt(index);
       if (!song) {
         res.status(400).json({ error: "Invalid queue index" });