feat: batch fix artist sort tags + rename folder when override is added

- edit-metadata: use albumArtistSort (when provided) for artist folder naming
  instead of auto-converted romajiAlbumArtist — ensures manual overrides sent
  by the download pipeline also place files in the correct folder
- Add POST /api/fix-artist-sort endpoint: searches Navidrome for all songs
  where artist or albumArtist matches the kanji, re-writes ARTISTSORT +
  ALBUMARTISTSORT via ffmpeg (-map_metadata 0 preserves all other existing
  tags), moves each file to the correct artist folder, cleans up empty old
  dirs, triggers Navidrome rescan — returns a job ID for progress tracking
- addRomajiOverrideUI: after saving a new override, calls fix-artist-sort and
  shows a job card with live progress

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

src/ui.js

@@ -89,7 +89,7 @@ function _renderRomajiOverrides() {
     </div>`
   ).join('');
 }
-export function addRomajiOverrideUI() {
+export async function addRomajiOverrideUI() {
   const k = (document.getElementById('ro-kanji')?.value  || '').trim();
   const v = (document.getElementById('ro-romaji')?.value || '').trim();
   if (!k || !v) { toast('⚠ Kanji und Romaji eingeben'); return; }
@@ -97,6 +97,20 @@ export function addRomajiOverrideUI() {
   document.getElementById('ro-kanji').value  = '';
   document.getElementById('ro-romaji').value = '';
   _renderRomajiOverrides();
+  // Batch-fix existing songs in the library
+  if (!S.cfg.backendUrl || !S.cfg.url || !S.cfg.user || !S.cfg.pass) return;
+  try {
+    const jobId = 'job_' + Date.now();
+    addJob(jobId, `Romaji-Fix: ${v}`, k, 'fix-sort');
+    const res = await fetch(`${S.cfg.backendUrl}/api/fix-artist-sort`, {
+      method: 'POST', headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ ndUrl: S.cfg.url, user: S.cfg.user, pass: S.cfg.pass, artistKanji: k, artistSort: v, jobId }),
+    });
+    if (!res.ok) throw new Error(`HTTP ${res.status}`);
+    pollJob(jobId);
+  } catch (e) {
+    toast('⚠ Fix-Artist-Sort: ' + e.message);
+  }
 }
 export function removeRomajiOverrideUI(kanji) {
   removeRomajiOverride(kanji);