Refactor admin stats API and charts data models for consistency

- Updated `AdminStatsResponse` with streamlined type annotations and added `AdminStatsData` type definition.
- Renamed chart data model fields (`totalUsers` → `total_users`, `activeUsers` → `active_users`, `members` → `value`, etc.) for alignment with backend naming conventions.
- Adjusted related test files to reflect updated data model structure.
- Improved readability of `AdminPage` component by reformatting destructuring in `useQuery`.

frontend/src/app/[locale]/admin/page.tsx

@@ -19,7 +19,11 @@ import { useQuery } from '@tanstack/react-query';
 import { getAdminStats } from '@/lib/api/admin';
 
 export default function AdminPage() {
-  const { data: stats, isLoading, error } = useQuery({
+  const {
+    data: stats,
+    isLoading,
+    error,
+  } = useQuery({
     queryKey: ['admin', 'stats'],
     queryFn: async () => {
       const response = await getAdminStats();

frontend/src/lib/api/admin.ts

@@ -23,15 +23,22 @@ export interface AdminStatsResponse {
   user_status: UserStatusData[];
 }
 
+export type AdminStatsData = {
+  body?: never;
+  path?: never;
+  query?: never;
+  url: '/api/v1/admin/stats';
+};
+
 /**
  * Admin: Get Dashboard Stats
  *
  * Get aggregated statistics for the admin dashboard (admin only)
  */
 export const getAdminStats = <ThrowOnError extends boolean = false>(
-    options?: Options<any, ThrowOnError>
+  options?: Options<AdminStatsData, ThrowOnError>
 ) => {
-    return (options?.client ?? apiClient).get<AdminStatsResponse, any, ThrowOnError>({
+  return (options?.client ?? apiClient).get<AdminStatsResponse, unknown, ThrowOnError>({
     responseType: 'json',
     security: [
       {

frontend/tests/components/charts/OrganizationDistributionChart.test.tsx

@@ -19,9 +19,9 @@ jest.mock('recharts', () => {
 
 describe('OrganizationDistributionChart', () => {
   const mockData: OrganizationDistributionData[] = [
-    { name: 'Engineering', members: 45, activeMembers: 42 },
-    { name: 'Marketing', members: 28, activeMembers: 25 },
-    { name: 'Sales', members: 35, activeMembers: 33 },
+    { name: 'Engineering', value: 45 },
+    { name: 'Marketing', value: 28 },
+    { name: 'Sales', value: 35 },
   ];
 
   it('renders chart card with title and description', () => {

frontend/tests/components/charts/UserGrowthChart.test.tsx

@@ -19,9 +19,9 @@ jest.mock('recharts', () => {
 
 describe('UserGrowthChart', () => {
   const mockData: UserGrowthData[] = [
-    { date: 'Jan 1', totalUsers: 100, activeUsers: 80 },
-    { date: 'Jan 2', totalUsers: 105, activeUsers: 85 },
-    { date: 'Jan 3', totalUsers: 110, activeUsers: 90 },
+    { date: 'Jan 1', total_users: 100, active_users: 80 },
+    { date: 'Jan 2', total_users: 105, active_users: 85 },
+    { date: 'Jan 3', total_users: 110, active_users: 90 },
   ];
 
   it('renders chart card with title and description', () => {