fix: show read-only detail view after vendor creation instead of staying in edit mode

frontend/src/pages/LieferantDetail.tsx

@@ -52,6 +52,8 @@ export default function LieferantDetail() {
     if (isNew) {
       setEditMode(true);
       setForm({ ...emptyForm });
+    } else {
+      setEditMode(false);
     }
   }, [isNew]);