功能：增加平台账号管理与管理员保护

frontend/src/layouts/MainLayout.tsx

@@ -74,6 +74,12 @@ const adminSections: SidebarSection[] = [
     icon: <ShopOutlined />,
     children: [{ key: 'shop-list', label: '平台商户', path: '/platform-merchants' }],
   },
+  {
+    key: 'accounts',
+    label: '账号管理',
+    icon: <UserOutlined />,
+    children: [{ key: 'platform-users', label: '平台账号', path: '/platform-users' }],
+  },
   {
     key: 'orders',
     label: '订单管理',
@@ -180,6 +186,7 @@ function getSelectedKey(pathname: string, search: string) {
   if (pathname.startsWith('/open-api')) return 'api-docs'
   if (pathname.startsWith('/api-debug')) return 'api-debug'
   if (pathname.startsWith('/platform-merchants')) return 'shop-list'
+  if (pathname.startsWith('/platform-users')) return 'platform-users'
   return 'dashboard'
 }