Implement Phase 2: product archive and shop loop templates (Bootstrap 5)

Add 15 Twig template overrides for the product archive and shop loop:
- archive-product: 3+9 grid layout with optional filter sidebar
- content-product: card component with hook-based content injection
- content-product-cat: category card with thumbnail
- product-searchform: input-group with search icon button
- loop/loop-start, loop-end: responsive row-cols grid
- loop/header: archive title with description hook
- loop/result-count: showing X-Y of Z with aria-relevant
- loop/orderby: form-select-sm sort dropdown
- loop/pagination: delegates to components/pagination.html.twig
- loop/no-products-found: alert-info empty state
- loop/add-to-cart: btn-primary-sm with AJAX data attributes
- loop/price: fw-semibold with sale/regular markup
- loop/rating: Bootstrap Icon stars (full, half, empty)
- loop/sale-flash: badge bg-danger positioned overlay

CSS additions: product card hover, sale badge z-index, star rating sizing,
price del/ins styling, WooCommerce grid reset.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/content-product.html.twig

@@ -0,0 +1,44 @@
+{#
+ # Product Content in Loop (Bootstrap 5 Override)
+ #
+ # Renders a single product card within the shop loop grid.
+ # Uses Bootstrap 5 card component with stretched-link.
+ #
+ # Expected context:
+ #   product - WC_Product object with:
+ #     .name           - Product name
+ #     .permalink      - Product URL
+ #     .image          - Product thumbnail HTML
+ #     .price_html     - Formatted price HTML
+ #     .rating_html    - Star rating HTML
+ #     .is_on_sale     - Whether product is on sale
+ #     .add_to_cart    - Add-to-cart button context
+ #
+ # WooCommerce PHP equivalent: content-product.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+<div class="col">
+    <article class="card h-100 shadow-sm product">
+        {{ do_action('woocommerce_before_shop_loop_item') }}
+
+        {# Product image with sale badge overlay #}
+        <div class="position-relative overflow-hidden">
+            {{ do_action('woocommerce_before_shop_loop_item_title') }}
+        </div>
+
+        <div class="card-body d-flex flex-column">
+            {# Product title #}
+            {{ do_action('woocommerce_shop_loop_item_title') }}
+
+            {# Rating and price #}
+            {{ do_action('woocommerce_after_shop_loop_item_title') }}
+        </div>
+
+        <div class="card-footer bg-transparent border-0 pt-0 pb-3 px-3">
+            {{ do_action('woocommerce_after_shop_loop_item') }}
+        </div>
+    </article>
+</div>