feat(admin-portal): 完成参考项目差距闭环 - 4 批次补齐 + Vitest 测试

差距分析闭环（workline §7-§8）：
- P0：审计子模块 3 页 + 学校组织 7 页
- P1：系统设置 4 Card + 公告管理 + 邀请码管理
- P2：文件管理 + AI 配置
- P6：5 测试文件 / 69 用例全过

共享基础设施：
- permissions +11 权限点 +14 路由
- view-models +20 接口
- i18n +100 key
- graphql-client +25 operation
- fixtures/handlers +15 mock +20 handler

质量：typecheck + lint 零错误，vitest 69/69 通过，arch.db 已更新

apps/admin-portal/src/hooks/use-files.ts

@@ -0,0 +1,102 @@
+/**
+ * 文件管理 Hooks
+ *
+ * contract §2.4：adminFiles / adminFileStats / deleteFiles
+ */
+import { useCallback, useState } from "react";
+import { useGraphMutation, useGraphQuery } from "./use-graphql";
+import {
+  ADMIN_FILES_QUERY,
+  ADMIN_FILE_STATS_QUERY,
+  DELETE_FILES_MUTATION,
+} from "@/lib/graphql-client";
+import type {
+  FileViewModel,
+  FileStats,
+  PaginatedResult,
+} from "@/types/view-models";
+
+/** 文件列表筛选参数 */
+export interface FileFilter {
+  page?: number;
+  pageSize?: number;
+  search?: string;
+  mimeType?: string;
+  entityType?: string;
+}
+
+interface AdminFilesResponse {
+  adminFiles: PaginatedResult<FileViewModel>;
+}
+
+interface AdminFileStatsResponse {
+  adminFileStats: FileStats;
+}
+
+interface DeleteFilesResponse {
+  deleteFiles: boolean;
+}
+
+export function useFiles(filter: FileFilter) {
+  const result = useGraphQuery<AdminFilesResponse>(ADMIN_FILES_QUERY, {
+    filter,
+  });
+  return {
+    ...result,
+    data: result.data?.adminFiles ?? null,
+  };
+}
+
+export function useFileStats() {
+  const result = useGraphQuery<AdminFileStatsResponse>(ADMIN_FILE_STATS_QUERY);
+  return {
+    ...result,
+    data: result.data?.adminFileStats ?? null,
+  };
+}
+
+export function useDeleteFiles() {
+  const [run, state] = useGraphMutation<DeleteFilesResponse, { ids: string[] }>(
+    DELETE_FILES_MUTATION,
+  );
+  const deleteFiles = useCallback(
+    async (ids: string[]) => {
+      const res = await run({ ids });
+      return res.data?.deleteFiles ?? false;
+    },
+    [run],
+  );
+  return [deleteFiles, state] as const;
+}
+
+/** 文件筛选状态管理 */
+export function useFileFilter(initial?: FileFilter) {
+  const [filter, setFilter] = useState<FileFilter>({
+    page: 1,
+    pageSize: 20,
+    ...initial,
+  });
+  const setPage = useCallback(
+    (page: number) => setFilter((f) => ({ ...f, page })),
+    [],
+  );
+  const setSearch = useCallback(
+    (search: string) => setFilter((f) => ({ ...f, search, page: 1 })),
+    [],
+  );
+  const setMimeType = useCallback(
+    (mimeType: string) =>
+      setFilter((f) => ({ ...f, mimeType: mimeType || undefined, page: 1 })),
+    [],
+  );
+  const setEntityType = useCallback(
+    (entityType: string) =>
+      setFilter((f) => ({
+        ...f,
+        entityType: entityType || undefined,
+        page: 1,
+      })),
+    [],
+  );
+  return { filter, setFilter, setPage, setSearch, setMimeType, setEntityType };
+}