Fix button text update when selecting product option

- Update button text from "Choisissez une option" to "Ajouter au panier" when option is selected
- Add data-default-text attribute to preserve translated text
- Improve UX by providing clear feedback when option is selected

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

assets/js/product-size.js

@@ -45,6 +45,12 @@
                 // Activer le bouton
                 addToCartButton.removeAttribute('disabled');
 
+                // Changer le texte du bouton
+                const buttonText = addToCartButton.querySelector('.txt');
+                if (buttonText) {
+                    buttonText.textContent = buttonText.getAttribute('data-default-text') || 'Ajouter au panier';
+                }
+
                 // Gérer la classe is-selected sur les li parents
                 allLi.forEach(li => li.classList.remove('is-selected'));
                 this.closest('li').classList.add('is-selected');