feat: romaji artist names, Apple Music autofill, romaji index invalidation

- Artist grid and detail header now show romaji names when toggle is on.
  Builds a Map<artistId, artistRomaji> from the existing song romaji index
  so no extra API call is needed.

- Apple Music autofill button added to edit modal next to MusicBrainz.
  Reuses the existing lookupItunesTrackMeta backend function via a new
  GET /api/itunes/lookup endpoint — fills album, year, genre, track#,
  and cover art.

- Romaji index is invalidated after every successful download so newly
  added songs appear with correct sort tags without requiring a page reload.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/views.js

@@ -6,7 +6,7 @@ import { playQueue, dlSongLocal, playPreview, toggleStar, parseArtists } from '.
 import { showCtxMenu, openEditPlModal, openDlModal, closeSidebar, switchNavMode } from './ui.js';
 import { closeNowPlaying, closeNpMenu } from './nowplaying.js';
 import { makeCard, makeAlbumCard, makeSongItem, makeGlobalTrackItem, mkSection } from './components.js';
-import { fetchRomajiIndex } from './api.js';
+import { fetchRomajiIndex, dispArtistById } from './api.js';
 import { loadSpotifyImporter } from './spotify.js';
 import { loadSoundCloudImporter } from './soundcloud.js';
 
@@ -283,9 +283,10 @@ export async function loadArtists() {
   try {
     const r = await api('getArtists');
     const all = (r.artists?.index || []).flatMap(i => i.artist || []);
+    if (S.cfg.showRomaji) await fetchRomajiIndex().catch(() => {});
     g.innerHTML = '';
     all.forEach(a => {
-      const c = makeCard(a.name, a.albumCount+' Alben', null, '🎤');
+      const c = makeCard(dispArtistById(a.id, a.name), a.albumCount+' Alben', null, '🎤');
       c.classList.add('artist-card');
       c.onclick = () => navigate('artist-detail', a);
       g.appendChild(c);
@@ -344,7 +345,7 @@ function _makeTopsongRow(s, num, subtitle, list, idx) {
 
 // ─── ARTIST DETAIL ───
 export async function loadArtistDetail(artist) {
-  document.getElementById('artist-detail-name').textContent = artist.name;
+  document.getElementById('artist-detail-name').textContent = dispArtistById(artist.id, artist.name);
   document.getElementById('artist-back-btn').onclick = () => _navGoBack();
 
   const hero   = document.getElementById('artist-detail-hero');