feat: move the whole metadata/search stack from iTunes to Deezer (1.3)

Apple's iTunes /search returns 403 from server/datacenter IPs, which had broken global
search, charts, album/artist/single downloads and the metadata-editor autofill in
production. Everything now sources metadata from Deezer (free, no key, more requests,
returns explicit versions + real artist images + durations). Web + Android share one
source, so an artist resolves to one consistent name everywhere. Deezer results are
mapped to the legacy "ItunesItem" shape, so the UI + download flow are unchanged.

Backend:
- New backend/lib/deezer.js: lookupTrackMeta, fetchAlbumTracks, searchAlbumTracks,
  fetchArtistAlbums (+ pure pickTrackMatch/mapAlbumTrack for tests).
- metadata.js drops the iTunes lookups; novasonic-server download paths (track, album,
  artist, playlist enrich, spotify artwork) + autofill now use Deezer.
- Artist download uses Deezer discography (real albums only), not the iTunes album search.
- Editor autofill endpoint /api/itunes/lookup -> /api/meta/lookup; removed the dead
  iTunes /search proxy and the Apple charts RSS proxy.
- backend/test/deezer.test.js: unit tests for numbering, mixed-artist album-artist
  stability, explicit flags, the Japanese-title match guard (npm test; RUN_LIVE=1 for live).

Web:
- api.js search/lookups already on Deezer; charts now use Deezer /chart. Artist cards
  show the real Deezer photo. Visible "iTunes"/"Apple Music" labels -> "Deezer"
  (search badge, charts badge, preview bar, editor button, artist heading). SW ns-v51.

Android:
- New DeezerModels.kt with Dz* models + mappers to ItunesItem/ItunesRssEntry.
- ItunesClient is Deezer-backed (search = tracks+albums+artists in parallel; album/artist
  lookups; /chart charts), same method signatures. Visible strings -> Deezer.

Docs: README, CLAUDE.md and CHANGELOG (1.3) updated; Platform Parity Matrix reflects the
shared Deezer source + Android non-local artist page.

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

src/views/detail.js

@@ -210,7 +210,7 @@ export async function loadArtistDetail(artist) {
       }
     }
     if(iTracks.length) {
-      const heading = topSongs.length ? 'Weltweit populär (iTunes)' : 'Populäre Titel';
+      const heading = topSongs.length ? 'Weltweit populär (Deezer)' : 'Populäre Titel';
       const sec = document.createElement('div');
       sec.innerHTML = `<div class="section-title" style="margin-top:${topSongs.length?'8px':'0'};margin-bottom:10px">${heading}</div>`;
       const list = document.createElement('div'); list.className = 'song-list'; list.style.marginBottom = '20px';

src/views/spotify.js

@@ -247,7 +247,7 @@ function _setEnrichStatus(done, current, total) {
   if (!el) return;
   if (done) {
     el.className = 'done';
-    el.innerHTML = '<svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5"><polyline points="20 6 9 17 4 12"/></svg> iTunes-Daten geladen';
+    el.innerHTML = '<svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5"><polyline points="20 6 9 17 4 12"/></svg> Deezer-Daten geladen';
     el.style.display = 'flex';
     el.style.opacity = '1';
     setTimeout(() => {
@@ -256,7 +256,7 @@ function _setEnrichStatus(done, current, total) {
     }, 2000);
   } else {
     el.className = '';
-    el.innerHTML = `<div class="enrich-spinner"></div> Lade iTunes-Daten… (${current}/${total})`;
+    el.innerHTML = `<div class="enrich-spinner"></div> Lade Deezer-Daten… (${current}/${total})`;
     el.style.display = 'flex';
     el.style.opacity = '1';
   }
@@ -274,7 +274,7 @@ async function _loadSpotifyTrackArtwork(tracks, listEl) {
     _setArt(el, url);
   });
 
-  // Enrich each track with iTunes data — same call as global search
+  // Enrich each track with Deezer data — same call as global search
   const CONC = 4;
   let enriched = 0;
   _setEnrichStatus(false, 0, tracks.length);
@@ -287,15 +287,15 @@ async function _loadSpotifyTrackArtwork(tracks, listEl) {
         const results = await itunesSearch(`${t.trackName} ${firstArtist}`, 'musicTrack', 1);
         const match = results[0];
         if (!match) return;
-        // Always safe to enrich: artwork, preview, explicit, iTunes artist name
+        // Always safe to enrich: artwork, preview, explicit, canonical artist name
         if (match.artworkUrl100)      t.artworkUrl100      = match.artworkUrl100;
         if (match.trackExplicitness)  t.trackExplicitness  = match.trackExplicitness;
         if (match.previewUrl)         t.previewUrl         = match.previewUrl;
-        // Store iTunes canonical name separately — keeps original Spotify/Japanese in artistName
+        // Store the Deezer canonical name separately — keeps original Spotify/Japanese in artistName
         // so the UI shows the original and YTM search uses the original channel name.
-        if (match.artistName) t.itunesArtistName = match.artistName;
-        // Only enrich album/duration if we're confident the iTunes match is the correct song.
-        // For Japanese titles we can't word-match, so we skip — the backend's lookupItunesTrackMeta
+        if (match.artistName) t.metaArtistName = match.artistName;
+        // Only enrich album/duration if we're confident the Deezer match is the correct song.
+        // For Japanese titles we can't word-match, so we skip — the backend's lookupTrackMeta
         // handles it with better matching. For ASCII titles, require at least one shared word.
         const JP_RE = /[ぁ-んァ-ン一-龯]/;
         const isJapanese = JP_RE.test(t.trackName);