Import components from CSV mapping

Add components to an existing draft data structure using a CSV file and column mapping. Multipart form with file (CSV) and payload (JSON string), or JSON body with upload_id (completed resumable upload) plus mapping fields. Payload shape: { delimiter, dry_run?, overwrite?, components: [{ name, label, column_type, csv_column, codelist?: { mode: global|from_csv, ... } }] }. Codelists created from CSV use maintainable id CL_{component_name} under the structure agency.