feat(admin): web admin panel — user CRUD, role assignment, system health (#150)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/admin-role-guard.tsx

@@ -0,0 +1,40 @@
+'use client';
+
+import { useRouter } from 'next/navigation';
+import { useEffect } from 'react';
+import { useSession } from '@/lib/auth-client';
+
+interface AdminRoleGuardProps {
+  children: React.ReactNode;
+}
+
+export function AdminRoleGuard({ children }: AdminRoleGuardProps): React.ReactElement | null {
+  const { data: session, isPending } = useSession();
+  const router = useRouter();
+
+  const user = session?.user as
+    | (NonNullable<typeof session>['user'] & { role?: string })
+    | undefined;
+
+  useEffect(() => {
+    if (!isPending && !session) {
+      router.replace('/login');
+    } else if (!isPending && session && user?.role !== 'admin') {
+      router.replace('/');
+    }
+  }, [isPending, session, user?.role, router]);
+
+  if (isPending) {
+    return (
+      <div className="flex min-h-screen items-center justify-center">
+        <div className="text-sm text-text-muted">Loading...</div>
+      </div>
+    );
+  }
+
+  if (!session || user?.role !== 'admin') {
+    return null;
+  }
+
+  return <>{children}</>;
+}