feat: 管理端板块管理与旧版数据导入，补充部署运营文档

- 新增管理端板块管理页面与后端接口（admin_board）
- 新增旧版数据导入：legacyimport 服务、导入面板、importusers 命令行工具
- 聊天用户卡片、板块图标等 UI 组件与界面优化
- 补充 about/公告/1Panel 部署等文档
- gitignore 排除 dist/ 构建产物与 .agents/ 本地工具目录

frontend/components/admin/AdminShell.tsx

@@ -1,4 +1,4 @@
-"use client";
+"use client";
 
 import Link from "next/link";
 import { usePathname, useRouter } from "next/navigation";
@@ -23,6 +23,7 @@ import {
   ChevronDown,
   FileText,
   CircleDollarSign,
+  Columns3,
 } from "lucide-react";
 import type { User } from "@/lib/api";
 import { apiAdminPendingCounts, apiLogout } from "@/lib/api";
@@ -30,6 +31,7 @@ import {
   canModerateAny,
   canAccessAdminMessages,
   isAdminOrAbove,
+  isOwner,
   isStaff,
   isSuperOrOwner,
   type RoleUserLike,
@@ -117,6 +119,17 @@ const NAV_GROUPS: NavGroup[] = [
       },
     ],
   },
+  {
+    title: "板块",
+    items: [
+      {
+        href: "/admin/boards",
+        label: "板块管理",
+        icon: Columns3,
+        visible: (u) => isOwner(u.role),
+      },
+    ],
+  },
   {
     title: "站点",
     items: [