feat: disambiguate same-name artists by Deezer fan count + show fans

Deezer's artist search doesn't rank by popularity, so a name collision (5 artists named
"Joji") returned a niche one first (62 fans) instead of the real Joji (559k) — the artist
page then loaded the wrong discography and owned songs didn't show as downloaded.

- api.js: _dzArtist carries fanCount (nb_fan); artist search sorts by fanCount desc.
- search.js: artist cards show the fan count as subtitle; fan count passed to the artist page.
- detail.js: pick the most-popular name match (not the first); for local Navidrome artists
  with a real collision (>=2 same-name candidates), tie-break by SONG OVERLAP — prefer the
  Deezer candidate whose top tracks actually overlap the library (each artist has different
  songs, so this nails the right person). Costs a few calls only on a collision.
- Artist hero shows "<n> Fans" (immediately for global-search artists, after match for local).
- Android: DzArtist.nb_fan + /search/artist sorted by nb_fan so the right artist is first.
- Also: web global-search "unavailable" message now says Deezer, not Apple. SW ns-v52.

Verified live against Deezer: both fan-sort and overlap select the real Joji (id 5078097).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'ns-v51';
+const CACHE = 'ns-v52';
 const PRECACHE = ['/', 'index.html', 'manifest.json', 'icon.svg'];
 const SKIP_PATHS = ['/rest/stream', '/rest/download', '/config.js'];
 // Auth token params stripped from cache keys so artwork survives across sessions/token refreshes.