refactor(admin): 管理后台 UI - 独立设计系统并与用户端隔离

把后台 token、Ant 主题、壳层控件和抽屉弹窗从用户工作台拆开，去掉树状侧栏装饰线，色板仍用原来的中性黑白台阶。

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/pages/admin/plugins/plugins-page.tsx

@@ -1,11 +1,11 @@
 import { App, Button, Input, Select } from "antd";
-import { Switch } from "@/components/ui/base/switch";
+import { Switch } from "@/pages/admin/ui/controls";
 import { AlipayCircleFilled, WechatFilled } from "@ant-design/icons";
 import type { ColumnsType } from "antd/es/table";
 import { CloudUpload, PlugZap, RefreshCw, Search, Trash2, UsersRound } from "lucide-react";
 import { useEffect, useMemo, useState } from "react";
 
-import { PaginationBar } from "@/components/layout/workspace-page";
+import { PaginationBar } from "@/pages/admin/components/admin-ui";
 import "@/lib/plugins/builtin";
 import { EAGLE_PLUGIN_ID } from "@/lib/plugins/builtin/eagle";
 import { RUNNINGHUB_PLUGIN_ID } from "@/lib/plugins/builtin/workflows";