feat(client): 委派管理页最小运营闭环（E7）

- 新增委派 API 封装与委派管理页面（创建/列表/撤销）
- 增加菜单入口与路由守卫（expense.proxy_manage）

client/src/api/delegations.ts

@@ -0,0 +1,59 @@
+import { apiRequestData } from "./http";
+
+export type DelegationStatus = "active" | "scheduled" | "expired" | "revoked";
+
+export type DelegationItem = {
+  id: string;
+  principalEmployeeId: string;
+  delegateEmployeeId: string;
+  scope: "reimbursement_submit" | "all";
+  validFrom: string;
+  validTo: string | null;
+  revokedAt: string | null;
+  createdAt: string;
+  status: DelegationStatus;
+};
+
+export type CreateDelegationRequest = {
+  delegateEmployeeId: string;
+  scope?: "reimbursement_submit" | "all";
+  validFrom?: string;
+  validTo?: string;
+};
+
+export type CreateDelegationResponse = {
+  delegation: DelegationItem;
+};
+
+export type FetchMyDelegationsResponse = {
+  status: "active" | "scheduled" | "expired" | "revoked" | "all";
+  initiated: DelegationItem[];
+  received: DelegationItem[];
+};
+
+export async function createDelegation(payload: CreateDelegationRequest) {
+  return apiRequestData<CreateDelegationResponse>("/api/delegations", {
+    method: "POST",
+    body: JSON.stringify(payload),
+  });
+}
+
+export async function fetchMyDelegations(status: FetchMyDelegationsResponse["status"] = "active") {
+  const params = new URLSearchParams();
+  if (status && status !== "active") {
+    params.set("status", status);
+  }
+  const query = params.toString();
+  return apiRequestData<FetchMyDelegationsResponse>(`/api/delegations/mine${query ? `?${query}` : ""}`);
+}
+
+export async function revokeDelegation(delegationId: string) {
+  return apiRequestData<{ delegation: DelegationItem; outcome: string }>(
+    `/api/delegations/${delegationId}/revoke`,
+    {
+      method: "POST",
+      body: JSON.stringify({}),
+    },
+  );
+}
+