fixes the middleware setup

frontend/src/store.ts

@@ -20,12 +20,12 @@ const store = configureStore({
     preference: prefSlice.reducer,
     conversation: conversationSlice.reducer,
   },
-  middleware: (getDefaultMiddleware) => [
-    ...getDefaultMiddleware(),
-    prefListenerMiddleware.middleware,
-  ],
+  middleware: (getDefaultMiddleware) =>
+    getDefaultMiddleware().concat(prefListenerMiddleware.middleware),
 });
 
 export type RootState = ReturnType<typeof store.getState>;
 export type AppDispatch = typeof store.dispatch;
 export default store;
+
+// TODO : use https://redux-toolkit.js.org/tutorials/typescript#define-typed-hooks everywere instead of direct useDispatch