Fix: Catalog sort dropdown

Hi team 👋

This MR fixes the sort dropdown on the catalogs page. I noticed that after selecting a new value, the UI would show a loading skeleton and the dropdown would not update the selection.

I’ve removed the loading skeleton from the header controls because including the loading state for the entire header was causing the dropdown component itself to remount and revert to its initial value. Now, only the catalog results section shows a loading skeleton. I've also done some minor css changes to make it more visually consistent.

Looking forward to your review!