feat: replace OpenSSL with native Blowfish decryption and add library rescan

- Replace OpenSSL subprocess with BouncyCastle native Blowfish CBC decryption
- Add automatic Subsonic library scan trigger after downloads (with 30s debounce)
- Improve error handling in DeezerMetadataService search methods
- Add comprehensive tests for download service, metadata service, and library service
- Increase test coverage from 13 to 32 tests

octo-fiesta/Models/MusicModels.cs

@@ -112,3 +112,12 @@ public class DownloadInfo
     public DateTime StartedAt { get; set; }
     public DateTime? CompletedAt { get; set; }
 }
+
+/// <summary>
+/// Statut du scan de bibliothèque Subsonic
+/// </summary>
+public class ScanStatus
+{
+    public bool Scanning { get; set; }
+    public int? Count { get; set; }
+}