fix: friendly error for Spotify editorial playlist 403

Backend returns {error:'EDITORIAL_PLAYLIST'} on 403 playlist routes.
Frontend shows a step-by-step workaround card instead of a red error.

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

backend/novasonic-server.js

@@ -276,6 +276,9 @@ app.post('/api/spotify/resolve', async (req, res) => {
     res.status(400).json({ error: `Unbekannter Typ: ${type}` });
   } catch(e) {
     console.error('[spotify/resolve]', e.message);
+    if (e.message.includes('403') && e.message.includes('/playlists/')) {
+      return res.status(403).json({ error: 'EDITORIAL_PLAYLIST' });
+    }
     res.status(500).json({ error: e.message });
   }
 });

src/spotify.js

@@ -66,13 +66,31 @@ export async function resolveSpotifyLink() {
     });
     if (!res.ok) {
       const err = await res.json().catch(() => ({}));
-      throw new Error(err.error || `HTTP ${res.status}`);
+      if (err.error === 'EDITORIAL_PLAYLIST') throw new Error('EDITORIAL_PLAYLIST');
+      throw new Error(err.error || err.message || `HTTP ${res.status}`);
     }
     const data = await res.json();
     window._spotifyResolved = data;
     if (data.skippedLocal > 0) toast(`${data.skippedLocal} lokale Datei(en) übersprungen (kein Stream verfügbar)`);
     _renderSpotifyPreview(data);
   } catch(e) {
+    if (e.message === 'EDITORIAL_PLAYLIST') {
+      inner.innerHTML = `<div style="padding:16px;background:var(--surface);border-radius:10px;border-left:3px solid #1DB954">
+        <div style="font-weight:600;margin-bottom:10px;color:#1DB954">💡 Editorial Playlist erkannt</div>
+        <div style="font-size:13px;line-height:1.6;color:var(--text2)">
+          Spotify hat den API-Zugriff auf eigene kuratierte Playlists
+          (wie "Today's Top Hits", "Discover Weekly" etc.) für Drittanbieter-Apps gesperrt.<br><br>
+          <strong style="color:var(--text)">Lösung:</strong>
+          <ol style="margin:8px 0 0 0;padding-left:20px">
+            <li>In Spotify die Playlist öffnen</li>
+            <li>Alle Tracks markieren (Strg+A)</li>
+            <li>Rechtsklick → "Zu Playlist hinzufügen" → "Neue Playlist"</li>
+            <li>Diese eigene Kopie hier importieren</li>
+          </ol>
+        </div>
+      </div>`;
+      return;
+    }
     if (e.message.includes('SPOTIFY_CLIENT_ID') ||
         e.message.includes('Credentials fehlen') ||
         e.message.includes('Spotify-Token-Fehler')) {