move global 404 page to app router

client/src/pages/404.tsx

@@ -1,14 +0,0 @@
-import { useRouter } from "next/router";
-import { useEffect } from "react";
-
-// Temporary. Move to app/ directory when it's supported
-
-export default function NotFound() {
-  const router = useRouter();
-
-  useEffect(() => {
-    router.replace("/");
-  });
-
-  return null;
-}