fix: resolve Japanese-path songs stored as romaji files

When Navidrome has a Japanese path in its DB but the file was saved with
a romaji filename by the download pipeline, the existing fallback chain
compared the Japanese title stem against romaji filenames and always
failed. Added _findFileByStemOrRomaji which converts the stem via
romajiForStorage before the final recursive search, covering all three
endpoints: edit-metadata, delete-song, song-sorttags.

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

backend/novasonic-server.js

@@ -116,6 +116,19 @@ function _findFileByStem(dir, titleStem, depth = 0) {
   return null;
 }
 
+// Like _findFileByStem but also tries a romaji-converted stem.
+// Handles the case where Navidrome has a Japanese path in its DB but the file
+// on disk was stored with a romaji filename by the download pipeline.
+function _findFileByStemOrRomaji(dir, stem) {
+  const direct = _findFileByStem(dir, stem);
+  if (direct) return direct;
+  try {
+    const rt = (romajiForStorage(stem) || '').toLowerCase().trim();
+    if (rt && rt !== stem) return _findFileByStem(dir, rt);
+  } catch {}
+  return null;
+}
+
 // ─── QUEUE ────────────────────────────────────────────────────────────────────
 let activeDownloads = 0;
 const downloadQueue = [];
@@ -730,7 +743,7 @@ app.get('/api/song-sorttags', async (req, res) => {
     const found      = rebased
       || _findFileRecursive(CONFIG.musicPath, fileName)
       || _findFileInDir(rebasedDir || path.dirname(filePath), fileName)
-      || _findFileByStem(CONFIG.musicPath, titleStem);
+      || _findFileByStemOrRomaji(CONFIG.musicPath, titleStem);
     if (found) filePath = found; else return res.status(404).json({ error: 'File not found' });
   }
   try {
@@ -865,7 +878,7 @@ app.post('/api/edit-metadata', async (req, res) => {
     const found = rebased
       || _findFileRecursive(CONFIG.musicPath, fileName)
       || _findFileInDir(rebasedDir || originalDir, fileName)
-      || _findFileByStem(CONFIG.musicPath, titleStem);
+      || _findFileByStemOrRomaji(CONFIG.musicPath, titleStem);
     if (found) { filePath = found; }
     else return res.status(404).json({ error: `File not found: ${filePath} (music root: ${CONFIG.musicPath})` });
   }
@@ -1053,7 +1066,7 @@ app.post('/api/delete-song', async (req, res) => {
     const found = _rebasePath(filePath, CONFIG.musicPath)
       || _findFileRecursive(CONFIG.musicPath, fileName)
       || _findFileInDir(path.dirname(filePath), fileName)
-      || _findFileByStem(CONFIG.musicPath, titleStem);
+      || _findFileByStemOrRomaji(CONFIG.musicPath, titleStem);
     if (found) filePath = found;
     else return res.status(404).json({ error: 'File not found on disk' });
   }