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/router/index.tsx

@@ -3,6 +3,7 @@ import { AppShellLayout } from "../layouts/AppShellLayout";
 import { AuthLayout } from "../layouts/AuthLayout";
 import { AuditLogsPage } from "../pages/AuditLogsPage";
 import { DashboardPage } from "../pages/DashboardPage";
+import { DelegationsPage } from "../pages/DelegationsPage";
 import { ForbiddenPage } from "../pages/ForbiddenPage";
 import { InvoicePoolPage } from "../pages/InvoicePoolPage";
 import { LoginPage } from "../pages/LoginPage";
@@ -93,6 +94,15 @@ export function AppRouter() {
           }
         />
 
+        <Route
+          path="delegations"
+          element={
+            <RequirePermission anyOf={["expense.proxy_manage"]}>
+              <DelegationsPage />
+            </RequirePermission>
+          }
+        />
+
         <Route path="settings/profile" element={<ProfilePage />} />
       </Route>