Add comprehensive SEO optimization

Implement complete SEO setup for virtual product pages with:
- Meta tags (title, description, canonical, hreflang)
- Open Graph protocol for social sharing
- Twitter Card tags
- Schema.org structured data (JSON-LD) for products
- XML sitemap including virtual pages
- Dynamic meta tag updates via JavaScript

Changes:
- Create SEO snippet with all meta tags
- Add structured data snippet for products
- Generate sitemap.xml with products and hreflang
- Update meta tags dynamically when Shopify data loads
- Remove noindex/nofollow (was blocking all indexing)
- Add product-specific OG tags (price, availability)

All pages now properly indexed with correct multilingual setup.

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

site/snippets/structured-data-product.php

@@ -0,0 +1,84 @@
+<?php
+/**
+ * Structured Data (JSON-LD) for Product pages
+ * This will be populated by JavaScript after Shopify data is loaded
+ */
+?>
+<script type="application/ld+json" id="product-schema">
+{
+  "@context": "https://schema.org/",
+  "@type": "Product",
+  "name": "<?= $page->title() ?>",
+  "description": "",
+  "image": [],
+  "offers": {
+    "@type": "Offer",
+    "url": "<?= $page->url() ?>",
+    "priceCurrency": "EUR",
+    "price": "0",
+    "availability": "https://schema.org/InStock",
+    "seller": {
+      "@type": "Organization",
+      "name": "Index.ngo"
+    }
+  },
+  "brand": {
+    "@type": "Organization",
+    "name": "Index.ngo"
+  }
+}
+</script>
+<script>
+// Update structured data when product loads
+(function() {
+  const container = document.querySelector('[data-product-loader]');
+  if (!container) return;
+
+  const handle = container.dataset.shopifyHandle;
+  const language = container.dataset.language || 'fr';
+  const isEnglish = language === 'en';
+
+  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;
+    const description = isEnglish && product.descriptionEn?.value ? product.descriptionEn.value : product.description;
+    const price = parseFloat(product.priceRange.minVariantPrice.amount);
+    const images = product.images.edges.map(edge => edge.node.url);
+    const availability = product.availableForSale ? 'https://schema.org/InStock' : 'https://schema.org/OutOfStock';
+
+    const schema = {
+      "@context": "https://schema.org/",
+      "@type": "Product",
+      "name": title,
+      "description": description,
+      "image": images,
+      "offers": {
+        "@type": "Offer",
+        "url": window.location.href,
+        "priceCurrency": "EUR",
+        "price": price.toFixed(2),
+        "availability": availability,
+        "seller": {
+          "@type": "Organization",
+          "name": "Index.ngo"
+        }
+      },
+      "brand": {
+        "@type": "Organization",
+        "name": "Index.ngo"
+      }
+    };
+
+    const schemaScript = document.getElementById('product-schema');
+    if (schemaScript) {
+      schemaScript.textContent = JSON.stringify(schema, null, 2);
+    }
+  });
+})();
+</script>