Place cover and artist images in library folders on upload import

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

services/api/internal/uploads/worker.go

@@ -343,6 +343,7 @@ func (s *Service) importFile(ctx context.Context, f File) error {
 			return fmt.Errorf("artist image: %w", err)
 		}
 	}
+	s.placeSidecars(ctx, f, pl, rel)
 	if err := s.store.CompleteImport(ctx, f.ID, pl.src.ID, rel, fileID); err != nil {
 		return err
 	}