Add product category tree sidebar to archive and single product pages (v0.1.7)

Hierarchical category navigation with collapsible sub-levels up to 3 levels
deep, using Bootstrap 5 list-group and collapse components. Sidebar renders
on both archive/shop and single product pages with responsive offcanvas on
mobile. Active category highlighting and ancestor auto-expand for intuitive
navigation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/global/category-tree-node.html.twig

@@ -0,0 +1,46 @@
+{#
+ # Single Category Tree Node (recursive)
+ #
+ # Renders one category with optional collapsible children.
+ # Included recursively by category-tree.html.twig.
+ #
+ # Expected context:
+ #   node  - Category node from wc_bootstrap_get_category_tree()
+ #   level - Current nesting depth (1-3)
+ #
+ # @package WcBootstrap
+ # @since 0.1.7
+ #}
+
+<li class="list-group-item px-0 py-1 border-0">
+    <div class="d-flex align-items-center">
+        <a href="{{ node.url }}"
+           class="category-tree-link d-block text-decoration-none py-1 px-2 rounded flex-grow-1{% if node.is_active %} active fw-semibold{% endif %}"
+           {% if node.is_active %}aria-current="page"{% endif %}>
+            <span class="ps-{{ (level - 1) * 2 }}">
+                {{ node.name }}
+            </span>
+            <span class="badge bg-body-secondary text-body-secondary rounded-pill ms-1 small">{{ node.count }}</span>
+        </a>
+        {% if node.children is not empty %}
+            <button class="btn btn-sm btn-link text-body-secondary p-0 ms-1 category-tree-toggle"
+                    type="button"
+                    data-bs-toggle="collapse"
+                    data-bs-target="#cat-{{ node.term_id }}"
+                    aria-expanded="{{ node.is_active or node.is_ancestor ? 'true' : 'false' }}"
+                    aria-controls="cat-{{ node.term_id }}"
+                    aria-label="{{ __('Toggle subcategories', 'wc-bootstrap') }}">
+                <i class="bi bi-chevron-down small" aria-hidden="true"></i>
+            </button>
+        {% endif %}
+    </div>
+
+    {% if node.children is not empty %}
+        <ul class="list-group list-group-flush collapse{{ node.is_active or node.is_ancestor ? ' show' : '' }}"
+            id="cat-{{ node.term_id }}">
+            {% for child in node.children %}
+                {% include 'global/category-tree-node.html.twig' with { node: child, level: level + 1 } only %}
+            {% endfor %}
+        </ul>
+    {% endif %}
+</li>