feat: stabilization + recipe edit/create UI

frontend/src/pages/PlaceholderPage.tsx

@@ -0,0 +1,9 @@
+import { EmptyState } from '../components/ui/EmptyState'
+
+export function PlaceholderPage({ title, icon }: { title: string; icon: string }) {
+  return (
+    <div className="p-4">
+      <EmptyState icon={icon} title={title} description="Kommt bald!" />
+    </div>
+  )
+}