feat(shop): 交易中心壳层 1:1 统一购物车/订单/收益

抽出 commerce header 与二级导航，购物车/订单/收益共用主站交易中心壳层；收益 stats 轻量化，降低独立电商后台观感。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

templates/pages/page-cart.php

@@ -42,11 +42,16 @@ $address_book = is_array($cart_view['address_book'] ?? null) ? $cart_view['addre
         data-currency-symbol="<?php echo esc_attr((string) ($cart_view['currency_symbol'] ?? '¥')); ?>"
         data-coupon-enabled="<?php echo !empty($cart_view['coupon_enabled']) ? '1' : '0'; ?>"
     >
+        <?php
+        if (function_exists('aksrt_render_commerce_page_header')) {
+            aksrt_render_commerce_page_header([
+                'title'    => __('购物车', 'aksrt'),
+                'subtitle' => __('在下单前确认地址、运费、优惠券和支付方式。', 'aksrt'),
+                'active'   => 'cart',
+            ]);
+        }
+        ?>
         <div class="aksrt-cart-page__header">
-            <div>
-                <h1 class="aksrt-cart-page__title"><?php esc_html_e('购物车', 'aksrt'); ?></h1>
-                <p class="aksrt-cart-page__subtitle"><?php esc_html_e('在下单前确认地址、运费、优惠券和支付方式。', 'aksrt'); ?></p>
-            </div>
             <?php if (!empty($pending_orders)) : ?>
                 <div class="aksrt-cart-page__pending">
                     <span class="aksrt-cart-page__pending-label"><?php esc_html_e('待支付订单', 'aksrt'); ?></span>