chore(admin-ui): merchants index uses page header

resources/views/admin/merchants/index.blade.php

@@ -29,6 +29,20 @@
     };
 @endphp
 
+<div class="page-header mb-20" data-page="admin.merchants.index">
+    <div class="page-header-main">
+        <div>
+            <div class="page-header-title">站点管理</div>
+            <div class="page-header-subtitle">总台视角的站点管理入口：开通、查看和维护 SaaS 站点主体，并联动订阅/平台订单做收费闭环治理。</div>
+        </div>
+        <div class="page-header-actions">
+            @if($safeBackForLinks !== '')
+                <a href="{!! $safeBackForLinks !!}" class="btn btn-secondary btn-sm">返回上一页（保留上下文）</a>
+            @endif
+        </div>
+    </div>
+</div>
+
 <details class="card mb-20 collapsible filters-card" data-role="collapsible" data-storage-key="admin.merchants.filters" open>
     <summary class="collapsible-summary filters-summary">
         <div class="flex-between items-center">