Apply dark mode preferences immediately

app/views/layouts/application.html.erb

@@ -18,6 +18,8 @@
           userTheme === 'dark' || ((userTheme === 'auto') && window.matchMedia('(prefers-color-scheme: dark)').matches)
         );
       }
+      const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
+      mediaQuery.addEventListener('change', applyDarkmode);
     </script>
   </head>