Round vinyl cover in player bar + larger mobile player

- player-art: border-radius 50% (circle), vinyl ring shadow, centre dot appears while spinning
- Mobile player height: 62px -> 74px, cover: 36px -> 46px

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'ns-v18';
+const CACHE = 'ns-v19';
 const PRECACHE = ['/', 'index.html', 'styles.css', 'app.js', 'sw.js', 'manifest.json', 'icon.svg'];
 const SKIP_URLS = ['/rest/stream', '/rest/download', '/config.js'];