Combined import / export LiveView for collections.
Import: three-step flow — upload → preview → done. Export: download all (or per-node) collections as CSV.
CSV format mirrors the Atrium simple format: title, description, thumbnail, collection_type, access_level, status, creator_name, resource_class, language, publisher, date_published, isbn, subject, location, condition, availability, total_items, legacy_item_code, metadata
legacy_item_code may be a single value or a semicolon-separated list of
legacy codes when total_items is greater than 1.