Refactor Admin and Settings UI to Ethereal Precision aesthetic and improve note import/export functionality

memento-note/app/(admin)/admin/settings/settings-header.tsx

@@ -6,10 +6,10 @@ export function SettingsHeader() {
   const { t } = useLanguage()
   return (
     <div>
-      <h1 className="text-3xl font-bold text-gray-900 dark:text-white">
+      <h1 className="text-2xl font-bold tracking-tight text-foreground">
         {t('admin.settings')}
       </h1>
-      <p className="text-gray-600 dark:text-gray-400 mt-1">
+      <p className="text-muted-foreground mt-1">
         {t('admin.settingsDescription')}
       </p>
     </div>