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>

styles.css

@@ -848,6 +848,8 @@ button:focus{outline:none}
 .artist-hero-pfp-initial{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;font-size:52px;font-weight:700;color:var(--text2);line-height:1}
 .artist-hero-info{min-width:0;flex:1;display:flex;align-items:flex-end;padding:20px 24px;background:linear-gradient(to left,rgba(7,7,15,.95) 0%,rgba(7,7,15,.1) 100%)}
 .artist-hero-name{font-size:26px;font-weight:800;letter-spacing:-0.5px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
+.artist-hero-fans{font-size:12px;font-weight:600;color:var(--text2);margin-top:3px;display:none}
+.artist-hero-fans.show{display:block}
 @media(max-width:768px){
   .artist-hero-bg{filter:brightness(0.75) saturate(0.85);transform:scale(1)}
   .artist-hero-pfp-wrap{display:none}