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/sitemap.php

@@ -0,0 +1,54 @@
+<?= '<?xml version="1.0" encoding="UTF-8"?>' ?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
+        xmlns:xhtml="http://www.w3.org/1999/xhtml">
+<?php
+$site = site();
+$kirby = kirby();
+
+// Static pages
+$pages = $site->index()->filterBy('template', 'in', ['home', 'error', 'thanks']);
+
+foreach ($pages as $p) {
+  foreach ($kirby->languages() as $lang) {
+    $url = $p->url($lang->code());
+?>
+  <url>
+    <loc><?= $url ?></loc>
+    <lastmod><?= $p->modified('c', 'date') ?></lastmod>
+    <changefreq>monthly</changefreq>
+    <priority><?= $p->isHomePage() ? '1.0' : '0.8' ?></priority>
+    <?php foreach ($kirby->languages() as $altLang): ?>
+    <xhtml:link rel="alternate" hreflang="<?= $altLang->code() ?>" href="<?= $p->url($altLang->code()) ?>" />
+    <?php endforeach ?>
+  </url>
+<?php
+  }
+}
+
+// Virtual product pages from Shopify
+$products = getShopifyProducts();
+foreach ($products as $product) {
+  foreach ($kirby->languages() as $lang) {
+    $url = $lang->code() == 'fr'
+      ? $site->url() . '/' . $product['handle']
+      : $site->url() . '/en/' . $product['handle'];
+?>
+  <url>
+    <loc><?= $url ?></loc>
+    <lastmod><?= date('c') ?></lastmod>
+    <changefreq>weekly</changefreq>
+    <priority>0.9</priority>
+    <?php foreach ($kirby->languages() as $altLang): ?>
+    <?php
+      $altUrl = $altLang->code() == 'fr'
+        ? $site->url() . '/' . $product['handle']
+        : $site->url() . '/en/' . $product['handle'];
+    ?>
+    <xhtml:link rel="alternate" hreflang="<?= $altLang->code() ?>" href="<?= $altUrl ?>" />
+    <?php endforeach ?>
+  </url>
+<?php
+  }
+}
+?>
+</urlset>