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/config/config.php

@@ -14,6 +14,17 @@ return [
     ],
 
     'routes' => [
+        // Sitemap
+        [
+            'pattern' => 'sitemap.xml',
+            'action' => function() {
+                $sitemap = page('home');
+                return new Kirby\Cms\Response(
+                    snippet('sitemap', ['page' => $sitemap], true),
+                    'application/xml'
+                );
+            }
+        ],
         // French products (default)
         [
             'pattern' => '(:any)',