Fix JSONID type conversions for yandex-music-api-go v0.0.0-20261018072517-d0173f795d2a

The new library version uses models.JSONID (custom string type) for ID
fields instead of plain string. Convert to string where IDs are passed
to functions expecting string or compared with string values.

Affected: client.go (GetTrackInfoWithPosition), downloader.go
(track.ID usage), monitor.go (track.ID, album.ID usage), storage.go
(album/track ID assignment).

internal/monitor/monitor.go

@@ -152,9 +152,9 @@ func (m *Monitor) checkArtistTracks(ctx context.Context, artistID int, artistNam
 
 		newTracks := 0
 		for _, track := range tracks {
-			if !m.storage.IsTrackDownloaded(track.ID) {
-				m.logger.Info("new track found", "track_id", track.ID, "artist", artistName)
-				result := m.downloader.DownloadTrack(ctx, track.ID)
+			if !m.storage.IsTrackDownloaded(string(track.ID)) {
+				m.logger.Info("new track found", "track_id", string(track.ID), "artist", artistName)
+				result := m.downloader.DownloadTrack(ctx, string(track.ID))
 				if result.Success {
 					newTracks++
 				} else {
@@ -190,10 +190,10 @@ func (m *Monitor) checkArtistAlbums(ctx context.Context, artistID int, artistNam
 
 		newAlbums := 0
 		for _, album := range albums {
-			albumIDStr := album.ID
+			albumIDStr := string(album.ID)
 			if !m.isAlbumDownloaded(albumIDStr, album.TrackCount) {
 				m.logger.Info("new album found", "album_id", albumIDStr, "title", album.Title, "artist", artistName)
-				results := m.downloader.DownloadAlbum(ctx, album.ID)
+				results := m.downloader.DownloadAlbum(ctx, string(album.ID))
 				success := false
 				for _, r := range results {
 					if r.Success {