wip: implement websocket chat service with Pydantic models and session management

app/ws.py

@@ -0,0 +1,11 @@
+"""Thin re-export module matching the suggested ``app/ws.py`` layout.
+
+The actual websocket router lives in :mod:`app.api.chat` (consistent with
+this project's convention of keeping all routers under ``app/api``). This
+module simply re-exports it so the chat service can also be wired up as
+``from app.ws import router``.
+"""
+
+from app.api.chat import router
+
+__all__ = ["router"]