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/product-searchform.html.twig

@@ -0,0 +1,32 @@
+{#
+ # Product Search Form (Bootstrap 5 Override)
+ #
+ # Renders the WooCommerce product search form as a Bootstrap 5 input-group.
+ #
+ # Expected context:
+ #   index - Unique form index (for multiple search forms on a page)
+ #
+ # WooCommerce PHP equivalent: product-searchform.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% set field_id = 'woocommerce-product-search-field-' ~ (index|default(0)) %}
+
+<form role="search" method="get" class="woocommerce-product-search" action="{{ home_url('/') }}">
+    <label class="visually-hidden" for="{{ field_id }}">{{ __('Search for:') }}</label>
+    <div class="input-group">
+        <input type="search"
+               id="{{ field_id }}"
+               class="form-control"
+               placeholder="{{ __('Search products&hellip;') }}"
+               value="{{ get_search_query() }}"
+               name="s" />
+        <button type="submit" class="btn btn-outline-primary" aria-label="{{ __('Search') }}">
+            <i class="bi bi-search" aria-hidden="true"></i>
+            <span class="d-none d-sm-inline ms-1">{{ __('Search') }}</span>
+        </button>
+    </div>
+    <input type="hidden" name="post_type" value="product" />
+</form>