Add Shopify variant options selector with circular radio buttons

- Implement dynamic option rendering from Shopify variant data
- Generate circular radio buttons for product variants (sizes, colors, etc.)
- Disable add-to-cart button until option is selected
- Display "Choisissez une option" text when option required
- Update button text and enable on option selection
- Add is-selected class to chosen option
- Handle disabled state for out-of-stock variants
- Restore btn__default button style with icon and text structure
- Add chooseOption translation key in FR/EN

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

site/languages/en.php

@@ -30,6 +30,7 @@ return [
         'loading' => 'Loading...',
         'productNotFound' => 'Product not found',
         'selectVariant' => 'Select',
+        'chooseOption' => 'Choose an option',
 
         // Blueprints - Home
         'home.title' => 'Home',