fix(web): 'Unknown Artist' download from artist page + rename itunes*→deezer* identifiers

Fix (the reported bug):
- Deezer's /artist/{id}/albums omits the artist object, so discography album cards had an
  empty artist name → the download modal fell back to the literal "Unknown Artist", which
  poisoned the yt-dlp search ("Unknown Artist <album>") and its artist/channel filter, failing
  with "Nicht eindeutig gefunden".
- deezerLookupArtistAlbums now backfills the known artist name (we're on that artist's page).
- openDlModal now defaults album cards to an ALBUM download (was always Track), so a one-click
  download no longer grabs an album as a single track named after the album.

Rename (requested cleanup, dependency-checked so nothing breaks):
- All frontend itunes* identifiers → deezer* (functions, the ItunesItem-shape field keys
  itunesData/itunesArtistId/itunesFanCount/itunesId, the itunes-album-detail route + DOM ids,
  the badge-itunes CSS class). The backend reads none of these fields, so the boundary is safe.
- Verified: build passes; route/DOM-id/CSS producer↔consumer all consistent; only the factual
  "Apple's iTunes /search 403" comments keep the historical name. SW ns-v62.

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

src/ui/components.js

@@ -75,7 +75,7 @@ export function makeSongItem(s, idx, list, { noArtistLink = false, singlePlay =
   return el;
 }
 
-// ─── GLOBAL TRACK ITEM (iTunes / Spotify results) ───
+// ─── GLOBAL TRACK ITEM (Deezer / Spotify results) ───
 export function makeGlobalTrackItem(t, idx, list) {
   const el = document.createElement('div');
   el.className = 'gtrack-item';

src/ui/downloads.js

@@ -1,13 +1,16 @@
 import { S } from '../state.js';
 import { esc, toast } from '../utils.js';
-import { api, fetchRomajiIndex, romajiConvert, getRomajiOverrides, invalidateRomajiIndex, itunesLookupAlbum } from '../api.js';
+import { api, fetchRomajiIndex, romajiConvert, getRomajiOverrides, invalidateRomajiIndex, deezerLookupAlbum } from '../api.js';
 import { _addNotif } from './notify.js';
 
 // ─── DOWNLOAD MODAL ───
 export function openDlModal(track) {
   if(!S.cfg.backendUrl) { toast('⚠ Kein Backend konfiguriert. Bitte in Einstellungen eintragen.'); return; }
-  S.downloadTarget = track; S.dlType = 'track';
-  document.querySelectorAll('.modal-opt').forEach(o => o.classList.toggle('selected', o.dataset.type==='track'));
+  // Album cards pass isAlbum → default the modal to an album download, not a single track named
+  // after the album (a one-click download of an album card used to grab it as one "track").
+  const _defType = track.isAlbum ? 'album' : 'track';
+  S.downloadTarget = track; S.dlType = _defType;
+  document.querySelectorAll('.modal-opt').forEach(o => o.classList.toggle('selected', o.dataset.type===_defType));
   const info = document.getElementById('dl-modal-info');
   const art = track.artworkUrl100 || track.artworkUrl60 || '';
   info.innerHTML = `${art ? `<div class="modal-art"><img src="${art}"></div>` : '<div class="modal-art" style="display:flex;align-items:center;justify-content:center;font-size:28px">🎵</div>'}
@@ -35,7 +38,7 @@ export async function executeDownload() {
     title:      _title,
     album:      _album,
     artworkUrl:  S.downloadTarget.artworkUrl100 || S.downloadTarget.artworkUrl60 || '',
-    itunesId:    S.downloadTarget.trackId || S.downloadTarget.collectionId || null,
+    deezerId:    S.downloadTarget.trackId || S.downloadTarget.collectionId || null,
     collectionId: S.downloadTarget.collectionId || null,
     explicit:    S.downloadTarget.trackExplicitness === 'explicit',
     trackNum:    S.downloadTarget.trackNumber    || undefined,
@@ -51,7 +54,7 @@ export async function executeDownload() {
   // request — the backend downloads that list directly (Apple's /search is 403, so no iTunes lookup).
   if (S.dlType === 'album' && payload.collectionId) {
     try {
-      const albumTracks = await itunesLookupAlbum(payload.collectionId);
+      const albumTracks = await deezerLookupAlbum(payload.collectionId);
       if (albumTracks.length) payload.tracks = albumTracks;
     } catch {}
   }