fix: iTunes Japanese artist lookup + sort tag editing in info modal

- views.js: skip ASCII word-match when artist name is non-ASCII so Japanese
  artists (e.g. ヨルシカ) resolve correctly to an iTunes artist ID
- index.html + styles.css: collapsible Sort-Tags section in edit modal
- ui.js: pre-fill sort fields from romaji index; include in save body
- novasonic-server.js: accept manual titleSort/artistSort/albumArtistSort/albumSort
  overrides; fall back to auto-computed romaji when not provided

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

src/views.js

@@ -378,8 +378,9 @@ export async function loadArtistDetail(artist) {
   const _queryWords = _normWords(artist.name);
   const iArtistResults = iArtistRes.status === 'fulfilled' ? (iArtistRes.value || []) : [];
   const iArtistMatch = iArtistResults.find(r => {
+    if (_queryWords.size === 0) return true; // non-ASCII name (e.g. Japanese) — trust iTunes ranking
     const rw = _normWords(r.artistName);
-    return _queryWords.size > 0 && [..._queryWords].every(w => rw.has(w));
+    return [..._queryWords].every(w => rw.has(w));
   });
   const itunesArtistId = knownItunes ?? iArtistMatch?.artistId ?? null;