Introduces a proper key-value table (article_type_ebay_mappings) that
explicitly maps each eBay aspect name to either an Article field
(manufacturer, modelNumber, …) or an AttributeDefinition, with a
required flag per mapping entry.
- New entity ArticleTypeEbayMapping with SOURCE_ARTICLE_FIELD / SOURCE_ATTRIBUTE
- ArticleType gains OneToMany ebayMappings collection with upsertEbayMapping()
- EbayAdapter.buildAspects() reads from the mapping table instead of implicit name-matching
- Import controller persists mappings via upsertEbayMapping() and syncs required attribute assignments
- Template shows active mappings card and article_field action option
- Migration 20260520100000 creates the new table, drops old JSON column
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>