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>

CHANGELOG.md

@@ -24,7 +24,8 @@ Versioning: two-part `MAJOR.MINOR` — each release bumps the minor (features an
 | Multi-artist navigation          | ✅        | ✅      |
 | Album detail page                | ✅        | ✅      |
 | Artist page (Navidrome)          | ✅        | ✅      |
-| Artist page (iTunes fallback)    | ✅        | ❌      |
+| Artist page (Deezer fallback)    | ✅        | ✅      |
+| Global search source             | Deezer    | Deezer  |
 | Concert events (Ticketmaster)    | ✅        | ✅      |
 | Genre browsing                   | ✅        | ✅      |
 | Global search                    | ✅        | ✅      |
@@ -55,6 +56,29 @@ Versioning: two-part `MAJOR.MINOR` — each release bumps the minor (features an
 
 ---
 
+## [1.3] — 2026-07-31
+
+Big change: **the entire metadata/search stack moved from Apple's iTunes to Deezer** — on web, backend downloads *and* Android. Apple's iTunes `/search` returns **403 from server/datacenter IPs**, which had broken global search, charts, artist/album/single downloads and the metadata-editor autofill in production. Deezer is free, needs no key, allows more requests, and returns explicit versions + real artist images + track durations. Web and Android now share the **same** source, so an artist resolves to one consistent name everywhere.
+
+### Changed
+- **Web + Android + Backend** — Global search, album/artist lookups, artist top tracks and the "Neu & Beliebt" charts all run on **Deezer** (`api.deezer.com`). Results are mapped to the existing item shape, so the UI is unchanged; artist cards now show real photos (iTunes artist entities had none)
+- **Backend (download)** — Single-track, album and **artist** downloads, plus the metadata-editor autofill, now enrich from Deezer:
+  - `backend/lib/deezer.js` — new module: `lookupTrackMeta`, `fetchAlbumTracks`, `searchAlbumTracks`, `fetchArtistAlbums`
+  - Album/artist `album_artist` still comes from the album-level artist (Deezer `album.artist`), keeping soundtracks from splitting
+  - Genre comes from the Deezer album (one album-level genre); per-track artist is preserved for mixed-artist albums
+  - The autofill endpoint moved `/api/itunes/lookup` → **`/api/meta/lookup`**
+- **Web + Android** — All user-visible "iTunes" / "Apple Music" labels are now "Deezer" (search badge, charts badge, preview bar, editor autofill button, artist "populär" heading)
+- **Backend** — Removed the dead iTunes `/search` proxy and the Apple charts RSS proxy; the Deezer proxy (`/api/deezer/*`) now also serves charts and the editor lookup
+
+### Added
+- **Backend** — Unit tests for the Deezer mapping/matching logic (`backend/test/deezer.test.js`, run with `npm test`), incl. per-track numbering, mixed-artist album-artist stability, explicit flags and the Japanese-title match guard. A live smoke test runs with `RUN_LIVE=1`
+
+### Notes
+- Deploy: `git pull`, then rebuild the frontend (`docker compose up -d --build novasonic-frontend`) and restart the backend (`docker compose restart novasonic-backend`). Service worker bumped to `ns-v51`
+- Titles a user picked stay as chosen; only derived fields (album, album-artist, genre, year, artwork) follow Deezer
+
+---
+
 ## [1.2] — 2026-07-25
 
 Follow-up to 1.1: web history navigation, correct download tagging for mixed-artist albums, and UI polish.