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/ui.js

@@ -1,6 +1,6 @@
 import { S } from './state.js';
 import { esc, formatDur, toast } from './utils.js';
-import { api, coverUrl, ndAuth, fetchRomajiIndex, romajiConvert, romajiLookup } from './api.js';
+import { api, coverUrl, ndAuth, fetchRomajiIndex, romajiConvert, romajiLookup, invalidateRomajiIndex } from './api.js';
 import { THEMES, applyTheme, getCurrentThemeId } from './themes.js';
 // Circular imports — safe (only used inside function bodies)
 import { playQueue, dlSongLocal, toggleStar, togglePlay, renderQueue, syncNpStar, updateStarBtn, npToggleStar, playCurrent, _syncNpDirect, setPlayIcon, nativeInsertAt, refreshDisplayMode } from './player.js';
@@ -444,6 +444,36 @@ export async function autofillMusicBrainz() {
   }
 }
 
+export async function autofillItunes() {
+  if (!S.cfg.backendUrl) { toast('⚠ Kein Backend konfiguriert'); return; }
+  const s = S.infoSong;
+  if (!s) return;
+  const artist = document.getElementById('ie-artist').value || s.artist || '';
+  const title  = document.getElementById('ie-title').value  || s.title  || '';
+  const status = document.getElementById('info-edit-status');
+  status.textContent = '🔍 Apple Music…';
+  try {
+    const r = await fetch(`${S.cfg.backendUrl}/api/itunes/lookup?artist=${encodeURIComponent(artist)}&title=${encodeURIComponent(title)}`);
+    const d = await r.json();
+    if (!d.found) { status.textContent = '❌ Kein Treffer auf iTunes'; return; }
+    if (d.album)       document.getElementById('ie-album').value = d.album;
+    if (d.genre)       document.getElementById('ie-genre').value = d.genre;
+    if (d.year)        document.getElementById('ie-year').value  = d.year;
+    if (d.trackNum)    document.getElementById('ie-track').value = d.trackNum;
+    if (d.totalTracks) document.getElementById('ie-total').value = d.totalTracks;
+    if (d.coverUrl) {
+      S._infoArtData = { url: d.coverUrl };
+      document.getElementById('info-edit-art-preview').innerHTML =
+        `<img src="${d.coverUrl}" style="width:100%;height:100%;object-fit:cover" onerror="this.parentNode.innerHTML='<div class=\\'no-art\\' style=\\'width:100%;height:100%;display:flex;align-items:center;justify-content:center;font-size:28px\\'>🎵</div>'">`;
+      status.textContent = '✅ Metadaten + Cover von Apple Music';
+    } else {
+      status.textContent = '✅ Metadaten von Apple Music (kein Cover)';
+    }
+  } catch (e) {
+    status.textContent = '❌ Fehler: ' + e.message;
+  }
+}
+
 export async function saveMetadata() {
   if (!S.cfg.backendUrl) { toast('⚠ Kein Backend konfiguriert'); return; }
   const s = S.infoSong;
@@ -890,6 +920,7 @@ async function pollJob(jobId) {
       });
       if (d.status === 'done') {
         toast(d.skipped ? `⏭ "${title}" bereits auf dem Server` : `✅ ${title} gespeichert!`);
+        if (!d.skipped) invalidateRomajiIndex();
       }
     }
   } catch { updateJob(jobId, 'error', 'Status-Abfrage fehlgeschlagen'); }