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>

templates/product-selector.twig

@@ -0,0 +1,65 @@
+{# Product Selector Template #}
+<div class="wc-composable-product-selector" data-product-id="{{ product_id }}" data-selection-limit="{{ selection_limit }}" data-pricing-mode="{{ pricing_mode }}" data-fixed-price="{{ fixed_price }}">
+
+    <div class="composable-header">
+        <h3>{{ __('Select Your Products') }}</h3>
+        <p class="selection-info">
+            {{ __('Choose up to') }} <strong>{{ selection_limit }}</strong> {{ __('items from the selection below.') }}
+        </p>
+    </div>
+
+    <div class="composable-products-grid">
+        {% for product in products %}
+        <div class="composable-product-item" data-product-id="{{ product.id }}" data-price="{{ product.price }}">
+            <div class="product-item-inner">
+                <label class="product-item-label">
+                    <input type="checkbox"
+                           name="composable_products[]"
+                           value="{{ product.id }}"
+                           class="composable-product-checkbox"
+                           data-product-id="{{ product.id }}"
+                           data-price="{{ product.price }}">
+
+                    {% if show_images and product.image_url %}
+                    <div class="product-item-image">
+                        <img src="{{ product.image_url }}" alt="{{ product.name|esc_attr }}">
+                    </div>
+                    {% endif %}
+
+                    <div class="product-item-details">
+                        <h4 class="product-item-name">{{ product.name|esc_html }}</h4>
+
+                        {% if show_prices %}
+                        <div class="product-item-price">
+                            {{ product.price_html|raw }}
+                        </div>
+                        {% endif %}
+                    </div>
+
+                    <span class="product-item-checkmark"></span>
+                </label>
+            </div>
+        </div>
+        {% endfor %}
+    </div>
+
+    {% if show_total %}
+    <div class="composable-total">
+        <div class="total-label">{{ __('Total Price:') }}</div>
+        <div class="total-price" data-currency="{{ currency_symbol }}">
+            {% if pricing_mode == 'fixed' %}
+                {{ currency_symbol }}{{ fixed_price }}
+            {% else %}
+                <span class="calculated-total">{{ currency_symbol }}0.00</span>
+            {% endif %}
+        </div>
+    </div>
+    {% endif %}
+
+    <div class="composable-actions">
+        <button type="button" class="button alt composable-add-to-cart" data-product-id="{{ product_id }}">
+            {{ __('Add to Cart') }}
+        </button>
+        <div class="composable-messages"></div>
+    </div>
+</div>