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

includes/Core/Bootstrap.php

@@ -24,6 +24,9 @@ use WooNooW\Core\Notifications\PushNotificationHandler;
 use WooNooW\Core\Notifications\EmailManager;
 use WooNooW\Core\ActivityLog\ActivityLogTable;
 use WooNooW\Branding;
+use WooNooW\Frontend\Assets as FrontendAssets;
+use WooNooW\Frontend\Shortcodes;
+use WooNooW\Frontend\TemplateOverride;
 
 class Bootstrap {
     public static function init() {
@@ -37,6 +40,11 @@ class Bootstrap {
         PushNotificationHandler::init();
         EmailManager::instance(); // Initialize custom email system
         
+        // Frontend (customer-spa)
+        FrontendAssets::init();
+        Shortcodes::init();
+        TemplateOverride::init();
+        
         // Activity Log
         ActivityLogTable::create_table();