fix: iTunes JP-first with US fallback; romaji filter in playlist/starred search

backend/lib/metadata.js

@@ -92,13 +92,15 @@ async function lookupItunesTrackMeta(artist, title) {
     // e.g. "don't rush - slowed" → search "don't rush" so iTunes finds the single
     const baseTitle = title.replace(/\s*[-–]\s*\S[^-]*$/, '').trim() || title;
     const searchTitle = baseTitle !== title ? baseTitle : title;
-    const url = `https://itunes.apple.com/search?term=${encodeURIComponent(artist + ' ' + searchTitle)}&media=music&entity=musicTrack&limit=10&country=jp&explicit=Yes`;
-    const results = await new Promise((resolve, reject) => {
+    const fetchItunes = (country) => new Promise((resolve, reject) => {
+      const url = `https://itunes.apple.com/search?term=${encodeURIComponent(artist + ' ' + searchTitle)}&media=music&entity=musicTrack&limit=10&country=${country}&explicit=Yes`;
       https.get(url, res => {
         let d = ''; res.on('data', c => d += c);
         res.on('end', () => { try { resolve(JSON.parse(d).results || []); } catch { reject(new Error('parse')); } });
       }).on('error', reject);
     });
+    let results = await fetchItunes('jp');
+    if (!results.length) results = await fetchItunes('us');
     const normT     = normalizeTitle(title);
     const normA     = (artist || '').toLowerCase().trim();
     // Split by space OR comma/semicolon/slash so "VXLLAIN, iGRES" → "vxllain" not "vxllain,"