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/en.php

@@ -13,7 +13,20 @@ return [
         'backToShop' => 'Back to shop',
         'supportText' => 'To support us, you can also',
         'makeDonation' => 'make a donation',
+
+        // Shop / Cart
         'addToCart' => 'Add to cart',
+        'cart' => 'Cart',
+        'cartEmpty' => 'Your cart is empty',
+        'total' => 'Total',
+        'checkout' => 'Checkout',
+        'remove' => 'Remove',
+        'inStock' => 'In stock',
+        'outOfStock' => 'Out of stock',
+        'addingToCart' => 'Adding...',
+        'addedToCart' => 'Added! ✓',
+        'errorAddToCart' => 'Error - Try again',
+        'closeCart' => 'Close cart',
 
         // Blueprints - Home
         'home.title' => 'Home',