fix: enhance back navigation in NotFoundPage component

frontend/src/app/not-found.tsx

@@ -12,7 +12,17 @@ export default function NotFoundPage() {
           Oops, the page you are looking for could not be found.
         </p>
       </div>
-      <Button onClick={() => window.history.back()} variant="secondary">
+      <Button
+        onClick={() => {
+          if (window.history.length > 1) {
+            window.history.back();
+          }
+          else {
+            window.location.href = "/";
+          }
+        }}
+        variant="secondary"
+      >
         Go Back
       </Button>
     </div>