Add i18n support and cart total to Shopify integration

Implement multilingual support for shop interface and add total calculation to cart drawer:
- Add FR/EN translations for all shop-related texts (cart, checkout, stock status)
- Update templates and JavaScript to use translation system
- Add cart total calculation with formatted currency display
- Refactor cart drawer styles to SASS with improved button styling (black borders on +/-)
- Fix English product content (replace JSON with proper HTML)
- Extract cart drawer to separate snippet for better organization

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

site/languages/fr.php

@@ -13,7 +13,20 @@ return [
         'backToShop' => 'Retour à la boutique',
         'supportText' => 'Pour nous soutenir, vous pouvez aussi',
         'makeDonation' => 'faire un don',
+
+        // Shop / Cart
         'addToCart' => 'Ajouter au panier',
+        'cart' => 'Panier',
+        'cartEmpty' => 'Votre panier est vide',
+        'total' => 'Total',
+        'checkout' => 'Passer commande',
+        'remove' => 'Retirer',
+        'inStock' => 'En stock',
+        'outOfStock' => 'Rupture de stock',
+        'addingToCart' => 'Ajout en cours...',
+        'addedToCart' => 'Ajouté ! ✓',
+        'errorAddToCart' => 'Erreur - Réessayer',
+        'closeCart' => 'Fermer le panier',
 
         // Blueprints - Home
         'home.title' => 'Accueil',