feat: 帖子分级置顶（板块/全站）与板块管理员置顶权限、消息管理权限调整

frontend/components/admin/AdminShell.tsx

@@ -32,6 +32,7 @@ import {
   Images,
   Link2,
   CodeXml,
+  Pin,
 } from "lucide-react";
 import type { User } from "@/lib/api";
 import { apiAdminPendingCounts, apiLogout } from "@/lib/api";
@@ -95,6 +96,12 @@ const NAV_GROUPS: NavGroup[] = [
         visible: (u) => canModerateAny(u),
         pendingBadge: true,
       },
+      {
+        href: "/admin/pinned",
+        label: "置顶管理",
+        icon: Pin,
+        visible: (u) => canModerateAny(u),
+      },
       {
         href: "/admin/messages",
         label: "消息管理",