fix: resolve silent voice playback on VPS and queue screenshare streams

- Call unpause() when starting a stream in DiscordPlayer to prevent getting stuck in a paused state.
- Call stop() instead of pause() in VoiceController on disconnect to fully reset the player.
- Add user-agent header to ffmpeg calls in MusicPlayer and Transcoder to prevent YouTube 403 Forbidden on VPS.
- Add screenshare streams to the media queue when successfully started.

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

src/player.ts

@@ -76,6 +76,7 @@ export class DiscordPlayer {
       this.setResourceVolume(nextVolume);
     }
     this.player.play(resource);
+    this.unpause(owner);
     this.connection?.subscribe(this.player);
   }