perf(14-01): add GPU promotion and containment to all scroll containers

- contain: layout style on :host of all 6 scroll-heavy components
- contain: paint + will-change: transform on all scroll containers for GPU compositing
- content-visibility: auto + contain-intrinsic-size on .album-card for off-screen skip
- cover-grid, track-list, queue-panel, artists-view, genres-view, playlist-view

frontend/src/components/playlist-view/playlist-view.ts

@@ -175,6 +175,7 @@ export class PlaylistView extends LitElement {
             flex-direction: column;
             overflow: hidden;
             position: relative;
+            contain: layout style;
         }
 
         .header {
@@ -306,6 +307,8 @@ export class PlaylistView extends LitElement {
             list-style: none;
             display: flex;
             flex-direction: column;
+            contain: paint;
+            will-change: transform;
         }
 
         .playlist-item {