Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/app/error.tsx

@@ -8,13 +8,7 @@ import { useEffect } from "react";
  * stays), shows a friendly card, and offers a reset. The raw error is logged to
  * the console, never shown to the user.
  */
-export default function Error({
-  error,
-  reset,
-}: {
-  error: Error & { digest?: string };
-  reset: () => void;
-}) {
+export default function Error({ error, reset }: { error: Error & { digest?: string }; reset: () => void }) {
   useEffect(() => {
     console.error(error);
   }, [error]);