Fix cart initialization and ShopifyCart loading

- Wait for ShopifyCart to be available before initializing structured data
- Add getCart() method to retrieve existing cart from Shopify API
- Load cart state on page load to display correct initial cart contents

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

site/snippets/structured-data-product.php

@@ -38,12 +38,18 @@
   const language = container.dataset.language || 'fr';
   const isEnglish = language === 'en';
 
-  const cart = new ShopifyCart({
-    domain: 'nv7cqv-bu.myshopify.com',
-    storefrontAccessToken: 'dec3d35a2554384d149c72927d1cfd1b'
-  });
+  function initStructuredData() {
+    if (typeof ShopifyCart === 'undefined') {
+      setTimeout(initStructuredData, 100);
+      return;
+    }
 
-  cart.getProductByHandle(handle).then(product => {
+    const cart = new ShopifyCart({
+      domain: 'nv7cqv-bu.myshopify.com',
+      storefrontAccessToken: 'dec3d35a2554384d149c72927d1cfd1b'
+    });
+
+    cart.getProductByHandle(handle).then(product => {
     if (!product) return;
 
     const title = isEnglish && product.titleEn?.value ? product.titleEn.value : product.title;
@@ -79,6 +85,10 @@
     if (schemaScript) {
       schemaScript.textContent = JSON.stringify(schema, null, 2);
     }
-  });
+    });
+  }
+
+  // Initialize when ShopifyCart is available
+  initStructuredData();
 })();
 </script>