- Adds a new `barcodes` connection on ProductVariant, allowing up to 20 barcodes per variant with type validation (UPC, EAN, ISBN, GTIN, ASIN).
- Enables reading and writing multiple barcodes via `productSet`, `productVariantsBulkCreate`, and `productVariantsBulkUpdate` mutations; the first barcode maps to the legacy `barcode` field.
- Deprecates the single `ProductVariant.barcode` field—reading returns the first barcode, writing updates it, but full multi‑barcode support is encouraged.