fix: Spotify locale URL support + improved token headers

- parseSpotifyUrl now handles intl-de/, intl-en/ and other locale prefixes
- getSpotifyToken uses full browser headers + sp_t cookie for the public endpoint

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

backend/novasonic-server.js

@@ -397,22 +397,29 @@ async function getSpotifyToken() {
     'https://open.spotify.com/get_access_token?reason=transport&productType=web_player',
     {
       headers: {
-        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36',
+        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36',
         Accept: 'application/json',
+        'Accept-Language': 'de-DE,de;q=0.9,en;q=0.8',
+        Cookie: 'sp_t=1',
+        Referer: 'https://open.spotify.com/',
+        'sec-fetch-dest': 'empty',
+        'sec-fetch-mode': 'cors',
+        'sec-fetch-site': 'same-origin',
       },
       signal: AbortSignal.timeout(8000),
     }
   );
-  if (!r.ok) throw new Error(`Spotify public token fehlgeschlagen (${r.status})`);
+  if (!r.ok) throw new Error(`Spotify token fehlgeschlagen (${r.status}) — Server-IP möglicherweise von Spotify geblockt`);
   const d = await r.json();
-  if (!d.accessToken) throw new Error('Kein Spotify-Token erhalten — Spotify möglicherweise nicht erreichbar');
+  if (!d.accessToken) throw new Error('Kein Spotify-Token erhalten');
   _spTok = d.accessToken;
   _spTokExp = d.accessTokenExpirationTimestampMs || (Date.now() + 3600000);
   return _spTok;
 }
 
 function parseSpotifyUrl(url) {
-  const m = url.match(/open\.spotify\.com\/(track|album|playlist)\/([A-Za-z0-9]+)/);
+  // Handles locale prefixes: open.spotify.com/intl-de/track/... or open.spotify.com/track/...
+  const m = url.match(/open\.spotify\.com\/(?:[a-z]{2,5}-[a-z]{2,5}\/)?(?:intl-[a-z-]+\/)?(track|album|playlist)\/([A-Za-z0-9]+)/);
   if (!m) throw new Error('Ungültige Spotify-URL — erwartet: open.spotify.com/track|album|playlist/...');
   return { type: m[1], id: m[2] };
 }