feat: Add product images support with WP Media Library integration

- Add WP Media Library integration for product and variation images
- Support images array (URLs) conversion to attachment IDs
- Add images array to API responses (Admin & Customer SPA)
- Implement drag-and-drop sortable images in Admin product form
- Add image gallery thumbnails in Customer SPA product page
- Initialize WooCommerce session for guest cart operations
- Fix product variations and attributes display in Customer SPA
- Add variation image field in Admin SPA

Changes:
- includes/Api/ProductsController.php: Handle images array, add to responses
- includes/Frontend/ShopController.php: Add images array for customer SPA
- includes/Frontend/CartController.php: Initialize WC session for guests
- admin-spa/src/lib/wp-media.ts: Add openWPMediaGallery function
- admin-spa/src/routes/Products/partials/tabs/GeneralTab.tsx: WP Media + sortable images
- admin-spa/src/routes/Products/partials/tabs/VariationsTab.tsx: Add variation image field
- customer-spa/src/pages/Product/index.tsx: Add gallery thumbnails display

customer-spa/package.json

@@ -40,6 +40,7 @@
     },
     "devDependencies": {
         "@hookform/resolvers": "^3.10.0",
+        "@types/node": "^22.0.0",
         "@types/react": "^18.3.5",
         "@types/react-dom": "^18.3.0",
         "@typescript-eslint/eslint-plugin": "^8.46.3",