fix: handle 429 rate-limit within timeout window

- Cap per-retry wait at 15s (Spotify's Retry-After can be very long)
- Increase global resolve timeout from 25s to 120s so retries can complete
- Log rate-limit waits for visibility

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

backend/novasonic-server.js

@@ -153,7 +153,9 @@ async function _spApi(path, token) {
   for (let attempt = 0; attempt < 4; attempt++) {
     const r = await _fetchTimeout(url, { headers: { Authorization: `Bearer ${token}` } });
     if (r.status === 429) {
-      const wait = (parseInt(r.headers.get('Retry-After') || '5', 10) + 1) * 1000;
+      const retryAfter = parseInt(r.headers.get('Retry-After') || '5', 10);
+      const wait = Math.min(retryAfter + 1, 15) * 1000; // cap at 15s per retry
+      console.log(`[spotify] 429 rate-limited, waiting ${wait / 1000}s (Retry-After: ${retryAfter}s)`);
       await new Promise(res => setTimeout(res, wait));
       continue;
     }
@@ -305,7 +307,7 @@ app.post('/api/spotify/resolve', async (req, res) => {
     console.log(`[spotify/resolve] ${type} ${id}`);
 
     const timeout = new Promise((_, reject) =>
-      setTimeout(() => reject(new Error('Zeitüberschreitung — Spotify API antwortet nicht (>25s)')), 25000)
+      setTimeout(() => reject(new Error('Zeitüberschreitung — Spotify API antwortet nicht (>120s)')), 120000)
     );
     const data = await Promise.race([_resolveSpotify(type, id), timeout]);
     res.json(data);