refactor(api): update auth routes to use roles list for guest check

Author: fulleni

routes/api/v1/auth/link-email.dart

@@ -22,7 +22,7 @@ Future<Response> onRequest(RequestContext context) async {
     // This should ideally be caught by `authenticationProvider` if route is protected
     throw const UnauthorizedException('Authentication required to link email.');
   }
-  if (authenticatedUser.role != UserRole.guestUser) {
+  if (!authenticatedUser.roles.contains(UserRoles.guestUser)) {
     throw const BadRequestException(
       'Account is already permanent. Cannot initiate email linking.',
     );