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>

src/api.js

@@ -305,6 +305,9 @@ function _dzArtist(a) {
     wrapperType: 'artist',
     artistId: a.id, artistName: a.name,
     artworkUrl100: a.picture_big || a.picture_medium || '',
+    // Deezer's artist search does NOT rank by popularity — several artists can share a name
+    // (5× "Joji"). fanCount lets us pick the one the user means (see itunesSearch + detail.js).
+    fanCount: a.nb_fan ?? undefined,
   };
 }
 
@@ -323,7 +326,9 @@ export async function itunesSearch(query, entity='musicTrack', limit=25) {
     const txt = await r.text();
     const data = (txt ? JSON.parse(txt) : {}).data || [];
     if (entity === 'album')      return data.map(_dzAlbum);
-    if (entity === 'musicArtist') return data.map(_dzArtist);
+    // Sort artists by popularity so a name collision resolves to the artist the user means
+    // (Deezer returns them in an unhelpful order — the real "Joji" isn't first).
+    if (entity === 'musicArtist') return data.map(_dzArtist).sort((x, y) => (y.fanCount || 0) - (x.fanCount || 0));
     return data.map(_dzTrack);
   } catch { _itunesLastError = 'network'; return []; }
 }