- Add SKU and GTIN fields to product variant repeater
- Render EAN/UPC barcode live from GTIN input (picqer/php-barcode-generator)
- Pull variant price from Shopify API instead of defaulting to 0
- Sync sku/gtin through EditProduct and CreateProduct save logic
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>