- Enhanced selectedMusicFolderIds helper to validate and filter library IDs
- Added ApplyLibraryFilter function in filter/filters.go for library filtering
- Updated getAlbumList to support musicFolderId parameter filtering
- Added comprehensive tests for multi-library functionality
- Supports single and multiple musicFolderId values
- Falls back to all accessible libraries when no musicFolderId provided
- Validates library access permissions for user security