style: 全站使用背景分层替代装饰边框并统一直角

src/App.vue

@@ -84,7 +84,6 @@ const menuOptions = computed<MenuOption[]>(() => [
         <a href="#main-content" class="skip-link">跳到主要内容</a>
         <NLayout has-sider class="admin-layout">
             <NLayoutSider
-                bordered
                 collapse-mode="width"
                 :collapsed="collapsed"
                 :width="208"
@@ -106,7 +105,7 @@ const menuOptions = computed<MenuOption[]>(() => [
                 />
             </NLayoutSider>
             <NLayout class="admin-main">
-                <NLayoutHeader bordered class="admin-topbar">
+                <NLayoutHeader class="admin-topbar">
                     <div class="flex min-w-0 items-center gap-3">
                         <NButton
                             quaternary