added admin system

src/components/Header.tsx

@@ -31,6 +31,14 @@ export function Header() {
                   <p className="text-xs text-blue-100 uppercase tracking-wide">Willkommen zurück</p>
                   <p className="text-sm font-semibold">{session.user?.email}</p>
                 </div>
+                {(session.user as any)?.admin && (
+                  <Link
+                    href="/admin"
+                    className="px-4 py-2 bg-yellow-500 hover:bg-yellow-600 active:bg-yellow-700 text-white font-semibold rounded-lg transition-all duration-200 transform hover:scale-105"
+                  >
+                    Admin
+                  </Link>
+                )}
                 <button
                   onClick={handleSignOut}
                   className="px-4 py-2 bg-red-600 hover:bg-red-700 active:bg-red-800 text-white font-semibold rounded-lg transition-all duration-200 transform hover:scale-105"