Add Bootstrap 5 single product page layout

Add two-column responsive grid (image gallery + product summary) for
single product pages, following the same bridge pattern used for
product archives.

Key changes:
- Create content-single-product.php bridge and Twig layout template
- Add single product renderer at template_redirect priority 11
- Disable WooCommerce block compatibility layer that strips classic
  hooks when parent theme has theme.json
- Move PHP templates to woocommerce/ subfolder for cleaner structure
- Fix Twig templates to self-compute context data not passed by
  wc_get_template() (tabs, short-description, meta, rating)
- Fix Underscore.js triple-brace syntax conflict in variation template
  by wrapping in {% verbatim %}

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

templates/content-single-product.html.twig

@@ -0,0 +1,56 @@
+{#
+ # Single Product Content (Bootstrap 5 Override)
+ #
+ # Renders the single product page with a Bootstrap 5 two-column grid:
+ #   Left column (col-lg-6):  Product images (sale flash + gallery)
+ #   Right column (col-lg-6): Product summary (title, rating, price, excerpt,
+ #                             add-to-cart, meta, sharing)
+ #   Full-width rows below:   Tabs, upsells, related products
+ #
+ # All individual components are rendered via WooCommerce action hooks,
+ # which trigger the Bootstrap 5 sub-templates through TemplateOverride.
+ #
+ # Rendered via the content-single-product.php bridge file (not TemplateOverride)
+ # because wc_get_template_part() does not fire the template_part hooks.
+ #
+ # Hook output structure:
+ #   woocommerce_before_single_product_summary → sale flash (10), product images (20)
+ #   woocommerce_single_product_summary        → title (5), rating (10), price (10),
+ #                                               excerpt (20), add-to-cart (30),
+ #                                               meta (40), sharing (50)
+ #   woocommerce_after_single_product_summary  → tabs (10), upsells (15), related (20)
+ #
+ # Context (from bridge file):
+ #   product       - WC_Product object
+ #   product_id    - Product post ID
+ #   product_class - Space-separated CSS class string from wc_get_product_class()
+ #
+ # WooCommerce PHP equivalent: content-single-product.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+<div id="product-{{ product_id }}" class="{{ product_class }}">
+
+    {# Two-column layout: images left, summary right #}
+    <div class="row g-4 g-lg-5 mb-5">
+        {# Left column: Sale flash + Product images #}
+        <div class="col-lg-6">
+            {{ do_action('woocommerce_before_single_product_summary') }}
+        </div>
+
+        {# Right column: Product summary #}
+        <div class="col-lg-6">
+            <div class="summary entry-summary">
+                {{ do_action('woocommerce_single_product_summary') }}
+            </div>
+        </div>
+    </div>
+
+    {# Full-width sections: Tabs, Upsells, Related Products #}
+    {{ do_action('woocommerce_after_single_product_summary') }}
+
+</div>
+
+{{ do_action('woocommerce_after_single_product') }}