make all books public by default (revert visibility gating)

backend/internal/storage/store.go

@@ -86,12 +86,11 @@ func (s *Store) WriteMetadata(ctx context.Context, meta domain.BookMeta) error {
 		return fmt.Errorf("WriteMetadata: %w", err)
 	}
 	if err == ErrNotFound {
-		// New scraped book — default to admin_only visibility.
 		postPayload := make(map[string]any, len(patchPayload)+1)
 		for k, v := range patchPayload {
 			postPayload[k] = v
 		}
-		postPayload["visibility"] = domain.VisibilityAdminOnly
+		postPayload["visibility"] = domain.VisibilityPublic
 		postErr := s.pb.post(ctx, "/api/collections/books/records", postPayload, nil)
 		if postErr == nil {
 			return nil