fix: 修复后台管理面板 UI 问题 — 移除多余分隔符竖线，用 flex 布局替代 calc() 高度计算

apps/server/src/routes/_protected/admin.tsx

@@ -1,6 +1,5 @@
 import { createFileRoute, Outlet } from '@tanstack/react-router'
 import { AdminSidebar } from '@/components/AdminSidebar'
-import { Separator } from '@/components/ui/separator'
 import { SidebarInset, SidebarProvider, SidebarTrigger } from '@/components/ui/sidebar'
 
 export const Route = createFileRoute('/_protected/admin' as never)({
@@ -14,11 +13,10 @@ function AdminLayout() {
       <SidebarInset>
         <header className="flex h-14 items-center gap-2 border-b px-6">
           <SidebarTrigger />
-          <Separator orientation="vertical" className="h-4" />
         </header>
-        <main className="flex-1 p-6">
+        <div className="flex min-h-0 flex-1 flex-col p-6">
           <Outlet />
-        </main>
+        </div>
       </SidebarInset>
     </SidebarProvider>
   )

apps/server/src/routes/_protected/admin/bookmarks.tsx

@@ -32,13 +32,13 @@ function BookmarksAdmin() {
   const selectedCategory = data.find((category: { id: string }) => category.id === selectedCategoryId)
 
   return (
-    <div className="space-y-6">
+    <div className="flex min-h-0 flex-1 flex-col gap-6">
       <div>
         <h1 className="text-2xl font-bold tracking-tight">书签管理</h1>
         <p className="text-muted-foreground">管理你的书签分类、图标和排序</p>
       </div>
 
-      <div className="flex h-[calc(100vh-8rem)] gap-6">
+      <div className="flex min-h-0 flex-1 gap-6">
         <div className="w-80 shrink-0">
           <CategoryManager
             categories={data}