Ajout des fichiers de l'application

src/app/not-found.tsx

@@ -0,0 +1,11 @@
+const NotFound = () => {
+  return (
+    <div className="not-found-page">
+      <div className="container page">
+        <p className="error-message">This page could not be found.</p>
+      </div>
+    </div>
+  );
+};
+
+export default NotFound;