Refactor and centralize user and pagination interfaces in useAdmin hook

- Unified `User` and `PaginationMeta` type definitions into `useAdmin` to improve maintainability and consistency.
- Updated affected components (`UserManagementContent`, `UserListTable`, `UserFormDialog`, `UserActionMenu`) to reference the centralized types.
- Enhanced test coverage for user-related hooks to include create, update, delete, activate, deactivate, and bulk actions.

frontend/src/components/admin/users/UserActionMenu.tsx

@@ -30,17 +30,9 @@ import {
   useActivateUser,
   useDeactivateUser,
   useDeleteUser,
+  type User,
 } from '@/lib/api/hooks/useAdmin';
 
-interface User {
-  id: string;
-  email: string;
-  first_name: string;
-  last_name: string | null;
-  is_active: boolean;
-  is_superuser: boolean;
-}
-
 interface UserActionMenuProps {
   user: User;
   isCurrentUser: boolean;

frontend/src/components/admin/users/UserFormDialog.tsx

@@ -26,6 +26,7 @@ import { toast } from 'sonner';
 import {
   useCreateUser,
   useUpdateUser,
+  type User,
 } from '@/lib/api/hooks/useAdmin';
 
 // ============================================================================
@@ -58,15 +59,6 @@ type UserFormData = z.infer<typeof userFormSchema>;
 // Component
 // ============================================================================
 
-interface User {
-  id: string;
-  email: string;
-  first_name: string;
-  last_name: string | null;
-  is_active: boolean;
-  is_superuser: boolean;
-}
-
 interface UserFormDialogProps {
   open: boolean;
   onOpenChange: (open: boolean) => void;

frontend/src/components/admin/users/UserListTable.tsx

@@ -29,25 +29,7 @@ import {
   SelectValue,
 } from '@/components/ui/select';
 import { UserActionMenu } from './UserActionMenu';
-
-interface User {
-  id: string;
-  email: string;
-  first_name: string;
-  last_name: string | null;
-  is_active: boolean;
-  is_superuser: boolean;
-  created_at: string;
-}
-
-interface PaginationMeta {
-  total: number;
-  page: number;
-  page_size: number;
-  total_pages: number;
-  has_next: boolean;
-  has_prev: boolean;
-}
+import type { User, PaginationMeta } from '@/lib/api/hooks/useAdmin';
 
 interface UserListTableProps {
   users: User[];

frontend/src/components/admin/users/UserManagementContent.tsx

@@ -10,7 +10,7 @@ import { useSearchParams, useRouter } from 'next/navigation';
 import { Plus } from 'lucide-react';
 import { Button } from '@/components/ui/button';
 import { useAuth } from '@/lib/auth/AuthContext';
-import { useAdminUsers } from '@/lib/api/hooks/useAdmin';
+import { useAdminUsers, type User, type PaginationMeta } from '@/lib/api/hooks/useAdmin';
 import { UserListTable } from './UserListTable';
 import { UserFormDialog } from './UserFormDialog';
 import { BulkActionToolbar } from './BulkActionToolbar';
@@ -30,13 +30,13 @@ export function UserManagementContent() {
   const [selectedUsers, setSelectedUsers] = useState<string[]>([]);
   const [dialogOpen, setDialogOpen] = useState(false);
   const [dialogMode, setDialogMode] = useState<'create' | 'edit'>('create');
-  const [editingUser, setEditingUser] = useState<any | null>(null);
+  const [editingUser, setEditingUser] = useState<User | null>(null);
 
   // Fetch users with query params
   const { data, isLoading } = useAdminUsers(page, 20);
 
-  const users = data?.data || [];
-  const pagination = data?.pagination || {
+  const users: User[] = data?.data || [];
+  const pagination: PaginationMeta = data?.pagination || {
     total: 0,
     page: 1,
     page_size: 20,
@@ -107,7 +107,7 @@ export function UserManagementContent() {
     setDialogOpen(true);
   };
 
-  const handleEditUser = (user: any) => {
+  const handleEditUser = (user: User) => {
     setDialogMode('edit');
     setEditingUser(user);
     setDialogOpen(true);

frontend/src/lib/api/hooks/useAdmin.tsx

@@ -123,6 +123,39 @@ export function useAdminStats() {
   });
 }
 
+/**
+ * Pagination metadata structure
+ */
+export interface PaginationMeta {
+  total: number;
+  page: number;
+  page_size: number;
+  total_pages: number;
+  has_next: boolean;
+  has_prev: boolean;
+}
+
+/**
+ * User interface matching backend UserResponse
+ */
+export interface User {
+  id: string;
+  email: string;
+  first_name: string;
+  last_name: string | null;
+  is_active: boolean;
+  is_superuser: boolean;
+  created_at: string;
+}
+
+/**
+ * Paginated user list response
+ */
+export interface PaginatedUserResponse {
+  data: User[];
+  pagination: PaginationMeta;
+}
+
 /**
  * Hook to fetch paginated list of all users (for admin)
  *
@@ -135,7 +168,7 @@ export function useAdminUsers(page = 1, limit = DEFAULT_PAGE_LIMIT) {
 
   return useQuery({
     queryKey: ['admin', 'users', page, limit],
-    queryFn: async () => {
+    queryFn: async (): Promise<PaginatedUserResponse> => {
       const response = await adminListUsers({
         query: { page, limit },
         throwOnError: false,
@@ -146,7 +179,7 @@ export function useAdminUsers(page = 1, limit = DEFAULT_PAGE_LIMIT) {
       }
 
       // Type assertion: if no error, response has data
-      return (response as { data: unknown }).data;
+      return (response as { data: PaginatedUserResponse }).data;
     },
     // Only fetch if user is a superuser (frontend guard)
     enabled: user?.is_superuser === true,