feat(saleor): Phase 1 - GraphQL Client Setup

- Add Apollo Client for Saleor GraphQL API
- Create GraphQL fragments (Product, Variant, Checkout)
- Create GraphQL queries (Products, Checkout)
- Create GraphQL mutations (Checkout operations)
- Add TypeScript types for Saleor entities
- Add product helper functions
- Install @apollo/client and graphql dependencies

Part of WordPress/WooCommerce → Saleor migration

package.json

@@ -9,9 +9,11 @@
     "lint": "eslint"
   },
   "dependencies": {
+    "@apollo/client": "^4.1.6",
     "@woocommerce/woocommerce-rest-api": "^1.0.2",
     "clsx": "^2.1.1",
     "framer-motion": "^12.34.4",
+    "graphql": "^16.13.1",
     "lucide-react": "^0.577.0",
     "next": "16.1.6",
     "next-intl": "^4.8.3",