refactor: 重构底层代码，抽离conn，调整消息处理器并创建传输层接口。

feature: 支持mqtt非桥接版本。

main/xiaozhi-server/plugins_func/functions/play_music.py

@@ -5,7 +5,7 @@ import random
 import difflib
 import traceback
 from pathlib import Path
-from core.handle.sendAudioHandle import send_stt_message
+# from core.handle.sendAudioHandle import send_stt_message  # 未使用，已移除
 from plugins_func.register import register_function, ToolType, ActionResponse, Action
 from core.utils.dialogue import Message
 from core.providers.tts.dto.dto import TTSMessageDTO, SentenceType, ContentType