fix: robust logout session clearing with cookie cleanup and isLoggingOut guard

- Clear next-auth session cookies directly as backup in logout page
- Add isLoggingOut localStorage flag to prevent TokenSync/PresenceProvider from restoring tokens
- Clear isLoggingOut flag on login page load as safety net
- Add createdAt to AgentSubscription interface (fixes build error)
- Add /education to public routes in middleware

src/components/layout/CommonHeader.tsx

@@ -280,6 +280,9 @@ export function CommonHeader() {
                     <button
                       onClick={() => {
                         setShowProfileMenu(false);
+                        // Set logout flag FIRST so TokenSync and PresenceProvider
+                        // don't restore tokens during the logout navigation
+                        localStorage.setItem('isLoggingOut', 'true');
                         localStorage.removeItem('accessToken');
                         localStorage.removeItem('refreshToken');
                         localStorage.removeItem('user');