refactor: 移除通用频道管理(LangBot)模块，IM Bot 改为直接对接；迁移 _call_real_llm 至 im_llm

backend/python/app/api/__init__.py

@@ -1,6 +1,5 @@
 from . import auth
 from . import chat
-from . import channels
 from . import knowledge
 from . import market
 from . import token_usage