fix: apply library filter to smart playlist track generation (#4739)

Smart playlists were including tracks from all libraries regardless of the
user's library access permissions. This resulted in ghost tracks that users
could not see or play, while the playlist showed incorrect song counts.

Added applyLibraryFilter to the refreshSmartPlaylist function to ensure only
tracks from libraries the user has access to are included when populating
smart playlist tracks. Added regression test to verify the fix.

Closes #4738

persistence/playlist_repository.go

@@ -264,6 +264,11 @@ func (r *playlistRepository) refreshSmartPlaylist(pls *model.Playlist) bool {
 		"annotation.item_id = media_file.id" +
 		" AND annotation.item_type = 'media_file'" +
 		" AND annotation.user_id = '" + usr.ID + "')")
+
+	// Only include media files from libraries the user has access to
+	sq = r.applyLibraryFilter(sq, "media_file")
+
+	// Apply the criteria rules
 	sq = r.addCriteria(sq, rules)
 	insSql := Insert("playlist_tracks").Columns("id", "playlist_id", "media_file_id").Select(sq)
 	_, err = r.executeSQL(insSql)