feat: self-service user signup (#672)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

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

@@ -0,0 +1,7 @@
+import type { PageLoad } from './$types';
+
+export const load: PageLoad = async ({ url }) => {
+	return {
+		token: url.searchParams.get('token') || undefined
+	};
+};