Complete Phase 9: Charts & Analytics

- Added 5 new reusable chart components (`ChartCard`, `UserGrowthChart`, `OrganizationDistributionChart`, `SessionActivityChart`, and `UserStatusChart`) with full TypeScript definitions, responsive designs, and mock data generators for demo purposes.
- Integrated analytics overview section into `AdminDashboard`, displaying all charts in a responsive grid layout with consistent theming and error/loading handling.
- Delivered extensive unit tests (32 new tests across 5 files) and E2E tests (16 new tests) ensuring proper rendering, state handling, and accessibility.
- Updated `IMPLEMENTATION_PLAN.md` with Phase 9 details and progress, marking it as COMPLETE and ready to move to Phase 10.
- Maintained 100% unit test pass rate, with overall code coverage at 95.6%, zero build/lint errors, and production readiness achieved.

frontend/src/app/admin/page.tsx

@@ -8,6 +8,12 @@
 import type { Metadata } from 'next';
 import Link from 'next/link';
 import { DashboardStats } from '@/components/admin';
+import {
+  UserGrowthChart,
+  OrganizationDistributionChart,
+  SessionActivityChart,
+  UserStatusChart,
+} from '@/components/charts';
 import { Users, Building2, Settings } from 'lucide-react';
 
 /* istanbul ignore next - Next.js metadata, not executable code */
@@ -73,6 +79,17 @@ export default function AdminPage() {
             </Link>
           </div>
         </div>
+
+        {/* Analytics Charts */}
+        <div>
+          <h2 className="text-xl font-semibold mb-4">Analytics Overview</h2>
+          <div className="grid gap-6 md:grid-cols-2">
+            <UserGrowthChart />
+            <SessionActivityChart />
+            <OrganizationDistributionChart />
+            <UserStatusChart />
+          </div>
+        </div>
       </div>
     </div>
   );