Initial implementation of WooCommerce Composable Products plugin

Implemented custom WooCommerce product type allowing customers to build their own
product bundles by selecting from predefined sets of products.

Features:
- Custom "Composable Product" type with admin interface
- Product selection by category, tag, or SKU
- Configurable selection limits (global and per-product)
- Dual pricing modes: fixed price or sum of selected products
- Modern responsive frontend with Twig templates
- AJAX add-to-cart functionality
- Full internationalization support (.pot file)
- WooCommerce settings integration
- Comprehensive documentation

Technical implementation:
- PHP 8.3+ with PSR-4 autoloading
- Twig 3.0 templating engine via Composer
- Vanilla JavaScript with jQuery for frontend interactions
- WordPress and WooCommerce hooks for seamless integration
- Security: input sanitization, validation, and output escaping
- Translation-ready with text domain 'wc-composable-product'

Documentation:
- README.md: Project overview and features
- INSTALL.md: Installation and usage guide
- IMPLEMENTATION.md: Technical architecture
- CHANGELOG.md: Version history

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

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

assets/css/frontend.css

@@ -0,0 +1,201 @@
+/**
+ * Frontend Styles for Composable Products
+ *
+ * @package WC_Composable_Product
+ */
+
+.wc-composable-product-selector {
+    margin: 2rem 0;
+    padding: 2rem;
+    background: #f9f9f9;
+    border-radius: 8px;
+}
+
+.composable-header {
+    margin-bottom: 2rem;
+    text-align: center;
+}
+
+.composable-header h3 {
+    margin: 0 0 0.5rem;
+    font-size: 1.5rem;
+    color: #333;
+}
+
+.selection-info {
+    margin: 0;
+    color: #666;
+    font-size: 0.95rem;
+}
+
+.composable-products-grid {
+    display: grid;
+    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
+    gap: 1.5rem;
+    margin-bottom: 2rem;
+}
+
+.composable-product-item {
+    position: relative;
+    background: #fff;
+    border: 2px solid #e0e0e0;
+    border-radius: 6px;
+    transition: all 0.3s ease;
+    cursor: pointer;
+}
+
+.composable-product-item:hover {
+    border-color: #999;
+    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
+}
+
+.composable-product-item.selected {
+    border-color: #2c3e50;
+    background: #f0f8ff;
+}
+
+.product-item-label {
+    display: block;
+    padding: 1rem;
+    cursor: pointer;
+    margin: 0;
+}
+
+.composable-product-checkbox {
+    position: absolute;
+    opacity: 0;
+    cursor: pointer;
+}
+
+.product-item-image {
+    margin-bottom: 1rem;
+    text-align: center;
+}
+
+.product-item-image img {
+    max-width: 100%;
+    height: auto;
+    border-radius: 4px;
+}
+
+.product-item-details {
+    text-align: center;
+}
+
+.product-item-name {
+    margin: 0 0 0.5rem;
+    font-size: 1rem;
+    font-weight: 600;
+    color: #333;
+}
+
+.product-item-price {
+    color: #666;
+    font-size: 0.9rem;
+}
+
+.product-item-checkmark {
+    position: absolute;
+    top: 0.5rem;
+    right: 0.5rem;
+    width: 24px;
+    height: 24px;
+    background: #fff;
+    border: 2px solid #ddd;
+    border-radius: 50%;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+}
+
+.composable-product-item.selected .product-item-checkmark::after {
+    content: '✓';
+    color: #2c3e50;
+    font-weight: bold;
+    font-size: 16px;
+}
+
+.composable-total {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 1.5rem;
+    background: #fff;
+    border-radius: 6px;
+    margin-bottom: 1.5rem;
+    font-size: 1.2rem;
+}
+
+.total-label {
+    font-weight: 600;
+    color: #333;
+}
+
+.total-price {
+    font-weight: 700;
+    color: #2c3e50;
+    font-size: 1.5rem;
+}
+
+.composable-actions {
+    text-align: center;
+}
+
+.composable-add-to-cart {
+    padding: 1rem 2rem;
+    font-size: 1.1rem;
+    min-width: 200px;
+}
+
+.composable-add-to-cart.loading {
+    opacity: 0.6;
+    cursor: wait;
+}
+
+.composable-messages {
+    margin-top: 1rem;
+}
+
+.composable-message {
+    padding: 1rem;
+    border-radius: 4px;
+    margin-bottom: 0.5rem;
+}
+
+.composable-message-error {
+    background: #fee;
+    color: #c00;
+    border: 1px solid #fcc;
+}
+
+.composable-message-success {
+    background: #efe;
+    color: #060;
+    border: 1px solid #cfc;
+}
+
+/* Responsive design */
+@media (max-width: 768px) {
+    .composable-products-grid {
+        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+        gap: 1rem;
+    }
+
+    .wc-composable-product-selector {
+        padding: 1rem;
+    }
+
+    .composable-total {
+        font-size: 1rem;
+    }
+
+    .total-price {
+        font-size: 1.2rem;
+    }
+}
+
+@media (max-width: 480px) {
+    .composable-products-grid {
+        grid-template-columns: 1fr;
+    }
+}