Fold AudioPlaybackManager into VoiceManager + Future-based play

- Move all static helpers (validate_voice_channel, prepare_source,
  prepare_audio_source, etc.) from AudioPlaybackManager into VoiceManager
- Add _play_await() using asyncio.Future + after callback, replacing
  all polling patterns and the 5-second sleep hack
- Add play() high-level method and play_source() for pre-made sources
- Unify connection logic under single _ensure_voice_client()
- Remove dead Voice cog class and its setup()
- Gut audio_playback.py to a re-export shim
- Remove cogs.voice from main.py extensions

1 files changed, 0 insertions, 1 deletions

diff --git a/main.py b/main.py
index 8f75ef4..cab1f54 100644
--- a/main.py
+++ b/main.py
@@ -75,7 +75,6 @@ if __name__ == "__main__":
         "cogs.trigger",
         "cogs.cron",
         "cogs.qr",
-        "cogs.voice",
         "cogs.uploader",
     ]