feat: delete song from disk via edit-metadata modal

- /api/delete-song endpoint: resolves path via same fallback chain as
  edit-metadata, validates file is inside music root + is an audio file,
  deletes it, then prunes the album folder if empty and the artist folder
  if that too becomes empty — no recursive rm, depth strictly limited to
  two levels above the file so no accidental mass-deletes
- Safety: path.resolve() guard ensures no path-traversal outside music root;
  rmdirSync (non-recursive) fails if dir is non-empty as extra safety net
- Frontend: delete button (red outline, trash icon) at bottom of edit mode
  with confirmation dialog showing title + folder-cleanup warning

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

src/main.js

@@ -45,7 +45,7 @@ import {
   toggleMobileSearch, closeMobileSearch, switchSetupTab,
   toggleNotifPanel, deleteNotif, clearNotifs, initNotifBell, _notifNavigate,
   _pickTheme,
-  toggleInfoEdit, onInfoArtFile, autofillMusicBrainz, autofillItunes, saveMetadata,
+  toggleInfoEdit, onInfoArtFile, autofillMusicBrainz, autofillItunes, saveMetadata, deleteSong,
 } from './ui.js';
 
 // ─── CONNECT ───
@@ -316,7 +316,7 @@ Object.assign(window, {
   loadSoundCloudImporter, resolveSoundCloudLink, clearSoundCloudPreview, scDlAll, scDlSingle, scDlTrack,
   executeSpotifyDownload, resolveYouTubeLink, executeYouTubeDownload,
   openPlModal, closePlModal, addSongsToPlaylist, createAndAddPlaylist, createPlaylistPrompt,
-  showSongInfo, closeInfoModal, toggleInfoEdit, onInfoArtFile, autofillMusicBrainz, autofillItunes, saveMetadata,
+  showSongInfo, closeInfoModal, toggleInfoEdit, onInfoArtFile, autofillMusicBrainz, autofillItunes, saveMetadata, deleteSong,
   openDlModal, closeDlModal, selectDlType, executeDownload,
   openEditPlModal, closeEditPlModal, saveEditPlaylist,
   editPlUploadCover, editPlCoverSelected, editPlRemoveCover, deletePlaylist, _confirmOk, _confirmCancel,

src/ui.js

@@ -515,6 +515,32 @@ export async function saveMetadata() {
   }
 }
 
+export async function deleteSong() {
+  if (!S.cfg.backendUrl) { toast('⚠ Kein Backend konfiguriert'); return; }
+  const s = S.infoSong;
+  if (!s?.id) return;
+  const ok = await showConfirm(
+    'Song löschen',
+    `"${s.title}" wird unwiderruflich von der Festplatte gelöscht. Leere Album- und Künstlerordner werden ebenfalls entfernt.`,
+    'Löschen'
+  );
+  if (!ok) return;
+  const status = document.getElementById('info-edit-status');
+  status.textContent = '🗑 Löschen…';
+  try {
+    const r = await fetch(`${S.cfg.backendUrl}/api/delete-song`, {
+      method: 'POST', headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ ndUrl: S.cfg.url, user: S.cfg.user, pass: S.cfg.pass, songId: s.id }),
+    });
+    const d = await r.json();
+    if (!r.ok) throw new Error(d.error || `HTTP ${r.status}`);
+    toast(`🗑 "${s.title}" gelöscht`);
+    closeInfoModal();
+  } catch (e) {
+    status.textContent = '❌ Fehler: ' + e.message;
+  }
+}
+
 // ─── DOWNLOAD MODAL ───
 export function openDlModal(track) {
   if(!S.cfg.backendUrl) { toast('⚠ Kein Backend konfiguriert. Bitte in Einstellungen eintragen.'); return; }