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/main.js

@@ -15,7 +15,7 @@ import {
 import {
   navigate, _navGoBack, _navOnPopState, _navLoad, onHeaderSearch, closeHeaderSearch,
   onGlobalSearch, s_goArtist, s_goAlbum, playerBarGoArtist, playerBarGoAlbum,
-  searchSimilarArtist, searchAndPreview, loadItunesAlbum, closeEventsModal,
+  searchSimilarArtist, searchAndPreview, loadDeezerAlbum, closeEventsModal,
   loadAlbums, loadStarred, loadRandom, filterStarred, filterPlaylist,
   plReorderEnter, plReorderSave, plReorderCancel, toggleAllGenres,
 } from './views/views.js';
@@ -314,7 +314,7 @@ Object.assign(window, {
   // Navigation
   navigate, onHeaderSearch, closeHeaderSearch, onGlobalSearch, s_goArtist, s_goAlbum,
   playerBarGoArtist, playerBarGoAlbum, searchSimilarArtist, searchAndPreview,
-  loadItunesAlbum, closeEventsModal,
+  loadDeezerAlbum, closeEventsModal,
   // Player
   playQueue, togglePlay, prevSong, nextSong, toggleShuffle, toggleRepeat,
   toggleQueue, setVolume, seekTo, starCurrent, downloadCurrent, playPreview,