refactor: rename site to frontend

frontend/src/pages/not-found-page.tsx

@@ -0,0 +1,20 @@
+import { Button, Paper, Text } from "@mantine/core";
+import { Layout } from "../components/layouts/layout";
+import { useTranslation } from "react-i18next";
+
+export const NotFoundPage = () => {
+  const { t } = useTranslation();
+  return (
+    <Layout>
+      <Paper shadow="md" p={30} mt={30} radius="md" withBorder>
+        <Text size="xl" fw={700}>
+          {t("notFoundTitle")}
+        </Text>
+        <Text>{t("notFoundSubtitle")}</Text>
+        <Button fullWidth mt="xl" onClick={() => window.location.replace("/")}>
+          {t("notFoundButton")}
+        </Button>
+      </Paper>
+    </Layout>
+  );
+};