Bundles a selection of style-order documents (by fileId) into a single ZIP archive and returns a signed download URL. Documents are those reachable from the style via its linked purchase/sales orders. Scoped to the caller's company; ids that do not resolve to a linked order for this style/company are rejected all-or-nothing with a 404 and details.fileIds listing the offending ids. A non-existent style returns style_not_found (404). An empty selection is rejected with a 400 by the route schema (min length 1) and again by the service as empty_file_ids.