fix: use bg-body on sign-up card for dark mode compatibility (#6973)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: talissoncosta

frontend/web/components/pages/HomePage.tsx

@@ -497,7 +497,7 @@ const HomePage: React.FC = () => {
                     ) : (
                       <>
                         <Card
-                          className='mb-3 bg-white p-3'
+                          className='mb-3 bg-body p-3'
                           contentClassName={classNames(
                             'd-flex flex-column gap-3',
                             { 'bg-light200': preventEmailPassword },