Fix critical Twig filter error in product selector template

Fixed "Unknown 'esc_attr' filter" error that occurred when rendering
the product selector template. The issue was caused by WordPress
escaping functions being registered only as Twig functions, not filters.

Changes:
- Added TwigFilter registrations for esc_html, esc_attr, esc_url
- Template now supports both filter syntax (|esc_attr) and function syntax
- Fixes compatibility issues when other plugins use their own Twig instances
- Version bump to 1.1.5

This resolves the bug documented in logs/fatal-errors-2025-12-31.log

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

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

wc-composable-product.php

@@ -3,7 +3,7 @@
  * Plugin Name: WooCommerce Composable Products
  * Plugin URI: https://github.com/magdev/wc-composable-product
  * Description: Create composable products where customers select a limited number of items from a configurable set
- * Version: 1.1.3
+ * Version: 1.1.5
  * Author: Marco Graetsch
  * Author URI: https://example.com
  * License: GPL v3 or later
@@ -19,7 +19,7 @@
 defined('ABSPATH') || exit;
 
 // Define plugin constants
-define('WC_COMPOSABLE_PRODUCT_VERSION', '1.1.3');
+define('WC_COMPOSABLE_PRODUCT_VERSION', '1.1.5');
 define('WC_COMPOSABLE_PRODUCT_FILE', __FILE__);
 define('WC_COMPOSABLE_PRODUCT_PATH', plugin_dir_path(__FILE__));
 define('WC_COMPOSABLE_PRODUCT_URL', plugin_dir_url(__FILE__));