feat: add a 404 route on frontend

frontend/src/NotFound.tsx

@@ -0,0 +1,12 @@
+import { Route } from "@tanstack/react-router";
+import { rootRoute } from "./main";
+
+const notFoundRoute = new Route({
+  getParentRoute: () => rootRoute,
+  path: "404",
+  component: () => {
+    return <span>404: Not Found</span>;
+  },
+});
+
+export default notFoundRoute;

frontend/src/main.tsx

@@ -21,6 +21,7 @@ import indexRoute from "./Home";
 import loginRoute from "./Login";
 import RootComponent from "./RootComponent";
 import viewTimetableRoute from "./ViewTimetable";
+import notFoundRoute from "./NotFound";
 import "./index.css";
 
 const queryClient = new QueryClient({
@@ -62,6 +63,7 @@ export const router = new Router({
   context: {
     queryClient,
   },
+  notFoundRoute: notFoundRoute,
 });
 
 // Register things for typesafety