feat(ux): sticky header on Albums, NewReleases, Artists

Header with search/sort/genre/year controls now pins to top while
scrolling, so filters stay reachable. Nested .content-body (App.tsx
wraps routes) was becoming the sticky anchor and swallowing the effect —
fixed with .content-body .content-body { overflow: visible }.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/styles/theme.css

@@ -4035,7 +4035,7 @@ select.input.input:focus {
 
   to {
     opacity: 1;
-    transform: translateY(0);
+    transform: none;
   }
 }