feat(hackathon): improve auth flow and UX

- Add email activation requirement for signup (no auto-login)
- Add form validation with React Hook Form and Zod on signup page
- Update callback page to handle email confirmation and password reset redirects
- Fix token format in API interceptor (use access_token)
- Fix middleware to use SessionToken for auth check
- Add infinite scroll with IntersectionObserver on browse teams page
- Replace all internal <a href> with <Link> components
- Add useInfiniteTeams hook for paginated team browsing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/hackathon/src/app/maintenance/page.tsx

@@ -1,3 +1,5 @@
+import { Link } from 'react-router';
+
 export default function MaintenancePage() {
   return (
     <div className="flex justify-center items-center min-h-screen bg-gray-50 dark:bg-gray-950 px-4">
@@ -9,12 +11,12 @@ export default function MaintenancePage() {
           <br />
           Thank you for your patience.
         </p>
-        <a
-          href="/"
+        <Link
+          to="/"
           className="mt-4 inline-block text-primary-600 hover:underline"
         >
           Back to Homepage
-        </a>
+        </Link>
       </div>
     </div>
   );