Reassociate sid and token when connecting websocket

If there are active background tasks for a given client_token, reassociate the
token and sid in the state when reconnecting so that updates from the
background task go to to the new websocket.

Author: masenf

reflex/app.py

@@ -2189,3 +2189,10 @@ async def link_token_to_sid(self, sid: str, token: str):
         if new_token:
             # Duplicate detected, emit new token to client
             await self.emit("new_token", new_token, to=sid)
+
+        # Update client state to apply new sid/token for running background tasks.
+        async with self.app.modify_state(
+            _substate_key(new_token or token, self.app.state_manager.state)
+        ) as state:
+            state.router_data[constants.RouteVar.SESSION_ID] = sid
+            state.router = RouterData.from_router_data(state.router_data)