feat: return not found. on /setup if already completed

frontend/src/routes/signup/setup/+page.ts

@@ -0,0 +1,18 @@
+import { error } from '@sveltejs/kit';
+import UserService from '$lib/services/user-service';
+import { AxiosError } from 'axios';
+import type { PageLoad } from './$types';
+
+export const load: PageLoad = async () => {
+	const userService = new UserService();
+
+	try {
+		await userService.checkInitialUserSetupAvailable();
+	} catch (e) {
+		if (e instanceof AxiosError && e.response?.status === 404) {
+			error(404, 'Not found');
+		}
+
+		throw e;
+	}
+};