fix(tracks): RC3 layout regressions + multi-artist links (#976)

* fix(tracks): RC3 layout regressions + multi-artist links

- Restore vertical rhythm on the Tracks hub: the header/hero/rails/browse
  sections sat two wrapper divs below .tracks-page so its flex gap never
  reached them and they collapsed together. New .tracks-hub-stack re-applies
  the gap, fixing the tagline-touching-hero and Random-Pick-overlapping-hero
  spacing (the rail's nav buttons no longer ride into the box above).
- Stop the sticky browse-table header going transparent on hover: its base
  background became opaque but the :hover rule still forced transparent, so
  rows bled through. Header now keeps its card background on hover.
- Widen the Duration column (56px -> 72px; 56 -> 64 on mobile) so the
  "DURATION" header no longer clips/overruns.
- Split multi-artist tracks into individually clickable artist links in both
  the "Track of the moment" hero and the browse list rows (OpenSubsonic
  artists[] with single-artist fallback), matching the album tracklist.

* docs(changelog): Tracks RC3 spacing, Duration, header hover, multi-artist (#976)

src/pages/SearchBrowsePage.tsx

@@ -852,7 +852,7 @@ export default function SearchBrowsePage() {
       data-advanced-search-root
     >
       <div style={{ visibility: isLeaveRestorePending ? 'hidden' : 'visible' }}>
-      <div>
+      <div className={showTracksChrome ? 'tracks-hub-stack' : undefined}>
       {showTracksChrome ? (
         <>
           <TracksPageChrome