fix: bump SW cache to v39, split multi-artists by ' / ', name-search fallback for artist nav

- sw.js: ns-v38 → ns-v39 forces PWA cache clear so previous fixes take effect
- components: split s.artist by ' / ' in makeSongItem — each part becomes its
  own clickable link; noArtistLink turns all parts into plain text
- views: s_goArtist searches Navidrome by name when no artistId is available
  (needed for secondary artists that only have the primary artistId in the song)

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

public/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'ns-v38';
+const CACHE = 'ns-v39';
 const PRECACHE = ['/', 'index.html', 'manifest.json', 'icon.svg'];
 const SKIP_PATHS = ['/rest/stream', '/rest/download', '/config.js'];