Implement Phase 4 & 5: cart and checkout templates (Bootstrap 5, HPOS)

Phase 4 - Cart (9 templates):
- cart: 8+4 column layout, table-responsive items, coupon input-group
- cart-empty: centered empty state with cart-x icon
- cart-item-data: inline dl for variation details
- cart-totals: card with list-group-flush rows, sticky sidebar
- cart-shipping: form-check radio per shipping method
- cross-sells: product loop grid section
- mini-cart: offcanvas-compatible item list with remove buttons
- proceed-to-checkout-button: btn-primary btn-lg w-100
- shipping-calculator: collapsible form with form-select/form-control

Phase 5 - Checkout (12 templates):
- form-checkout: 7+5 column layout, sticky order review sidebar
- form-billing: card with field wrapper, optional account creation
- form-shipping: card with ship-to-different-address collapse toggle
- form-coupon: collapsible input-group with alert-info toggle
- form-login: collapsible login reusing global/form-login.html.twig
- review-order: card with table-sm, tfoot subtotal/shipping/total
- payment: list-group of payment gateways with radio selection
- payment-method: form-check with description collapse
- terms: form-check checkbox with T&C link
- thankyou: HPOS compatible, alert-success + order details list-group
- order-received: confirmation message
- cart-errors: alert-danger with return-to-cart button

All order data accessed via WC_Order methods (HPOS compatible).
CSS additions: cart thumbnail sizing, checkout form field overrides,
payment box transitions, dark mode focus states.

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

templates/cart/cart-totals.html.twig

@@ -0,0 +1,82 @@
+{#
+ # Cart Totals (Bootstrap 5 Override)
+ #
+ # Renders the cart totals as a Bootstrap card with list-group rows.
+ #
+ # Expected context:
+ #   cart          - WC()->cart object (subtotal, fees, coupons, shipping, total)
+ #   cart_subtotal - Pre-rendered subtotal HTML
+ #   cart_total    - Pre-rendered total HTML
+ #   coupons       - Array of applied coupon objects
+ #   fees          - Array of fee objects
+ #
+ # WooCommerce PHP equivalent: cart/cart-totals.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+<div class="cart_totals">
+    {{ do_action('woocommerce_before_cart_totals') }}
+
+    <div class="card shadow-sm">
+        <div class="card-header">
+            <h2 class="h5 mb-0">{{ __('Cart totals') }}</h2>
+        </div>
+
+        <ul class="list-group list-group-flush">
+            {# Subtotal #}
+            <li class="list-group-item d-flex justify-content-between">
+                <span>{{ __('Subtotal') }}</span>
+                <span>{{ cart_subtotal|default(cart.get_cart_subtotal())|raw }}</span>
+            </li>
+
+            {# Coupons #}
+            {% if coupons is defined %}
+                {% for coupon in coupons %}
+                    <li class="list-group-item d-flex justify-content-between">
+                        <span>{{ __('Coupon:') }} {{ coupon.code|esc_html }}</span>
+                        <span>{{ coupon.discount_html|raw }}</span>
+                    </li>
+                {% endfor %}
+            {% endif %}
+
+            {# Shipping #}
+            {{ do_action('woocommerce_cart_totals_before_shipping') }}
+
+            {% if wc_shipping_enabled() is defined and wc_shipping_enabled() %}
+                <li class="list-group-item cart-shipping">
+                    {{ do_action('woocommerce_cart_totals_shipping') }}
+                </li>
+            {% endif %}
+
+            {{ do_action('woocommerce_cart_totals_after_shipping') }}
+
+            {# Fees #}
+            {% if fees is defined %}
+                {% for fee in fees %}
+                    <li class="list-group-item d-flex justify-content-between">
+                        <span>{{ fee.name|esc_html }}</span>
+                        <span>{{ fee.total_html|raw }}</span>
+                    </li>
+                {% endfor %}
+            {% endif %}
+
+            {{ do_action('woocommerce_cart_totals_before_order_total') }}
+
+            {# Order total #}
+            <li class="list-group-item d-flex justify-content-between fw-bold fs-5">
+                <span>{{ __('Total') }}</span>
+                <span>{{ cart_total|default(cart.get_total())|raw }}</span>
+            </li>
+
+            {{ do_action('woocommerce_cart_totals_after_order_total') }}
+        </ul>
+
+        <div class="card-body">
+            {{ do_action('woocommerce_proceed_to_checkout') }}
+        </div>
+    </div>
+
+    {{ do_action('woocommerce_after_cart_totals') }}
+</div>