- Pass quality parameter to /tracks/{track_id}/download-info API request
- Add GetTrackDownloadURL method that resolves signed download URLs by
downloading XML from download_info_url, parsing host/path/ts/s,
computing MD5 signature (salt: XGRlBW9FXlekgbPrRHuSiA), and
returning https://{host}/get-mp3/{sign}/{ts}{path}
- Add DownloadInfoURL field to DownloadInfo model for the XML URL
- Update DownloadTrack to use GetDirectLink resolution when URL is empty
- Port signing logic from yandex-music-api-python download_info.py