fix: log Spotify resolve errors to console

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

backend/novasonic-server.js

@@ -473,6 +473,7 @@ app.post('/api/spotify/resolve', async (req, res) => {
 
     res.status(400).json({ error: `Unbekannter Typ: ${type}` });
   } catch(e) {
+    console.error('[spotify/resolve]', e.message);
     res.status(500).json({ error: e.message });
   }
 });