Add admin hooks, components, and tests for statistics, navigation, and access control

- Introduced `useAdminStats`, `useAdminUsers`, and `useAdminOrganizations` hooks for admin data fetching with React Query.
- Added `AdminSidebar`, `Breadcrumbs`, and related navigation components for the admin section.
- Implemented comprehensive unit and integration tests for admin components.
- Created E2E tests for admin access control, navigation, and dashboard functionality.
- Updated exports to include new admin components.

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

@@ -0,0 +1,152 @@
+/**
+ * Admin Hooks
+ * React Query hooks for admin operations
+ *
+ * TODO - Stats Optimization (Option A):
+ * Currently calculating stats from multiple endpoints (Option B).
+ * For better performance at scale, consider implementing a dedicated
+ * /api/v1/admin/stats endpoint that returns pre-calculated counts
+ * to avoid fetching full lists.
+ */
+
+'use client';
+
+import { useQuery } from '@tanstack/react-query';
+import { adminListUsers, adminListOrganizations } from '@/lib/api/client';
+
+/**
+ * Admin Stats interface
+ */
+export interface AdminStats {
+  totalUsers: number;
+  activeUsers: number;
+  totalOrganizations: number;
+  totalSessions: number; // TODO: Requires admin sessions endpoint
+}
+
+/**
+ * Hook to fetch admin statistics
+ * Calculates stats from existing endpoints (Option B)
+ *
+ * @returns Admin statistics including user and organization counts
+ */
+export function useAdminStats() {
+  return useQuery({
+    queryKey: ['admin', 'stats'],
+    queryFn: async (): Promise<AdminStats> => {
+      // Fetch users list
+      // Use high limit to get all users for stats calculation
+      const usersResponse = await adminListUsers({
+        query: {
+          page: 1,
+          limit: 10000, // High limit to get all users for stats
+        },
+        throwOnError: false,
+      });
+
+      if ('error' in usersResponse) {
+        throw new Error('Failed to fetch users');
+      }
+
+      // Type assertion: if no error, response has data
+      const usersData = (usersResponse as { data: { data: Array<{ is_active: boolean }>; pagination: { total: number } } }).data;
+      const users = usersData?.data || [];
+      const totalUsers = usersData?.pagination?.total || 0;
+      const activeUsers = users.filter((u) => u.is_active).length;
+
+      // Fetch organizations list
+      const orgsResponse = await adminListOrganizations({
+        query: {
+          page: 1,
+          limit: 10000, // High limit to get all orgs for stats
+        },
+        throwOnError: false,
+      });
+
+      if ('error' in orgsResponse) {
+        throw new Error('Failed to fetch organizations');
+      }
+
+      // Type assertion: if no error, response has data
+      const orgsData = (orgsResponse as { data: { pagination: { total: number } } }).data;
+      const totalOrganizations = orgsData?.pagination?.total || 0;
+
+      // TODO: Add admin sessions endpoint
+      // Currently no admin-level endpoint exists to fetch all sessions
+      // across all users. The /api/v1/sessions/me endpoint only returns
+      // sessions for the current user.
+      //
+      // Once backend implements /api/v1/admin/sessions, uncomment below:
+      // const sessionsResponse = await adminListSessions({
+      //   query: { page: 1, limit: 10000 },
+      //   throwOnError: false,
+      // });
+      // const totalSessions = sessionsResponse.data?.pagination?.total || 0;
+
+      const totalSessions = 0; // Placeholder until admin sessions endpoint exists
+
+      return {
+        totalUsers,
+        activeUsers,
+        totalOrganizations,
+        totalSessions,
+      };
+    },
+    // Refetch every 30 seconds for near real-time stats
+    refetchInterval: 30000,
+    // Keep previous data while refetching to avoid UI flicker
+    placeholderData: (previousData) => previousData,
+  });
+}
+
+/**
+ * Hook to fetch paginated list of all users (for admin)
+ *
+ * @param page - Page number (1-indexed)
+ * @param limit - Number of records per page
+ * @returns Paginated list of users
+ */
+export function useAdminUsers(page = 1, limit = 50) {
+  return useQuery({
+    queryKey: ['admin', 'users', page, limit],
+    queryFn: async () => {
+      const response = await adminListUsers({
+        query: { page, limit },
+        throwOnError: false,
+      });
+
+      if ('error' in response) {
+        throw new Error('Failed to fetch users');
+      }
+
+      // Type assertion: if no error, response has data
+      return (response as { data: unknown }).data;
+    },
+  });
+}
+
+/**
+ * Hook to fetch paginated list of all organizations (for admin)
+ *
+ * @param page - Page number (1-indexed)
+ * @param limit - Number of records per page
+ * @returns Paginated list of organizations
+ */
+export function useAdminOrganizations(page = 1, limit = 50) {
+  return useQuery({
+    queryKey: ['admin', 'organizations', page, limit],
+    queryFn: async () => {
+      const response = await adminListOrganizations({
+        query: { page, limit },
+        throwOnError: false,
+      });
+
+      if ('error' in response) {
+        throw new Error('Failed to fetch organizations');
+      }
+
+      // Type assertion: if no error, response has data
+      return (response as { data: unknown }).data;
+    },
+  });
+}