fix(dz): implement alternative track fallback for error 2002

("Track token has
no sufficient rights on requested media").

Previous behavior:
- Only tried format fallback (FLAC → MP3_320 → MP3_128)
- Used same track token for all format attempts
- Failed when error 2002 occurred even if alternative tracks existed

New behavior:
- When error 2002 occurs, fetches FALLBACK.SNG_ID and gets fresh token
- Retries with same format but different track ID
- Loops through all alternative track IDs before trying format fallback
- Only after exhausting alternatives does it fall back to lower quality formats

src/lib/services/deezer.ts

@@ -438,7 +438,7 @@ export class DeezerAPI {
   }
 
   // Get track download URL
-  async getTrackDownloadUrl(trackToken: string, format: string, licenseToken: string, retryCount: number = 0): Promise<string | null> {
+  async getTrackDownloadUrl(trackToken: string, format: string, licenseToken: string, retryCount: number = 0): Promise<{ url: string | null; errorCode?: number; errorMessage?: string }> {
     console.log('[DEBUG] Getting track download URL...', { trackToken, format, licenseToken });
 
     try {
@@ -479,19 +479,19 @@ export class DeezerAPI {
         if (trackData.errors && trackData.errors.length > 0) {
           const error = trackData.errors[0];
           console.error('[ERROR] Deezer media API error:', error);
-          // Return null to trigger fallback, don't throw - let caller handle it
-          return null;
+          // Return error details so caller can handle alternative track fallback
+          return { url: null, errorCode: error.code, errorMessage: error.message };
         }
 
         if (trackData.media && trackData.media.length > 0) {
           const url = trackData.media[0].sources[0].url;
           console.log('[DEBUG] Got download URL:', url);
-          return url;
+          return { url };
         }
       }
 
       console.error('[ERROR] No download URL in response:', result);
-      return null;
+      return { url: null };
     } catch (error: any) {
       console.error('[ERROR] Failed to get track download URL:', error);