feat(chat): support public channel chat

app/dependencies/database.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from collections.abc import AsyncIterator, Callable
 from contextvars import ContextVar
 import json
 
@@ -51,6 +52,17 @@ async def get_db():
         yield session
 
 
+DBFactory = Callable[[], AsyncIterator[AsyncSession]]
+
+
+async def get_db_factory() -> DBFactory:
+    async def _factory() -> AsyncIterator[AsyncSession]:
+        async with AsyncSession(engine) as session:
+            yield session
+
+    return _factory
+
+
 # Redis 依赖
 def get_redis():
     return redis_client