Refactor 404 page to improve error message and button styling

packages/studiocms_dashboard/src/routes/404.astro

@@ -17,7 +17,8 @@ import { Layout } from '../components';
         <path d="M114 339V597C114 633.451 143.549 663 180 663H451.5V760C451.5 772.15 441.65 782 429.5 782H32C19.8497 782 10 772.15 10 760V361C10 348.85 19.8497 339 32 339H114Z" stroke="currentColor" stroke-width="20"/>
       </svg>
     </div>
-    <h2>Error 404 - Page not found</h2>
+    <h1>Error 404</h1>
+    <h2>Page not found</h2>
     <p>The page you are looking for might have been removed had its name changed or is temporarily unavailable.</p>
     <Button id="back-button" variant={'outlined'} color="primary" class="return" fullWidth><span>Go back</span></Button>
   </div>