## Description Artworks with missing or empty artist names currently appear first when sorting by artist A–Z. These are displayed as “Unknown artist” in the frontend. Place artworks with missing, empty or whitespace-only artist names, or the value “Unknown”, last in both artist sorting directions. ## Done when - [ ] Artworks with known artists are sorted A–Z or Z–A as selected. - [ ] Unknown artists appear last in both directions. - [ ] ID remains a secondary sort field for stable ordering. - [ ] Sorting is applied before pagination. - [ ] Search, filtering and `totalCount` continue to work correctly. - [ ] Title sorting and default ordering remain unchanged. - [ ] API tests cover both directions and pagination with unknown artists.