添加长期存储，流式检查

frontend/state.py

@@ -60,6 +60,8 @@ class AppState:
         """
         st.session_state.user_id = username.strip() if username.strip() else config.default_user_id
         st.session_state.logged_in = True
+        # 登录后必须开启一个干净的新对话
+        AppState.start_new_thread()
     
     @staticmethod
     def logout():
@@ -67,6 +69,8 @@ class AppState:
         st.session_state.logged_in = False
         st.session_state.user_id = config.default_user_id
         st.session_state.threads = []
+        # 登出后必须开启一个干净的新对话
+        AppState.start_new_thread()
     
     # ==================== 线程相关 ====================