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/loop/header.html.twig

@@ -0,0 +1,25 @@
+{#
+ # Product Archive Header (Bootstrap 5 Override)
+ #
+ # Renders the archive page title and optional description.
+ #
+ # Expected context:
+ #   show_page_title     - Whether to display the title (boolean, filtered)
+ #   page_title          - Archive page title string
+ #   archive_description - Optional archive description HTML
+ #
+ # WooCommerce PHP equivalent: loop/header.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+<header class="woocommerce-products-header mb-4">
+    {% if show_page_title is not defined or show_page_title %}
+        <h1 class="woocommerce-products-header__title page-title mb-2">
+            {{ page_title|default('')|esc_html }}
+        </h1>
+    {% endif %}
+
+    {{ do_action('woocommerce_archive_description') }}
+</header>