feat: URL preview TDS styling, settings description update

- UrlPreview.tsx: add data-url-preview attribute for CSS targeting
- lotus-terminal.css.ts: dark cyan border-left accent + transparent bg
  for URL preview cards in TDS mode (dark + light variants)
- General.tsx: mention Escape-to-skip in boot animation description

src/app/components/url-preview/UrlPreview.tsx

@@ -4,7 +4,7 @@ import { Box, as } from 'folds';
 import * as css from './UrlPreview.css';
 
 export const UrlPreview = as<'div'>(({ className, ...props }, ref) => (
-  <Box shrink="No" className={classNames(css.UrlPreview, className)} {...props} ref={ref} />
+  <Box shrink="No" data-url-preview="" className={classNames(css.UrlPreview, className)} {...props} ref={ref} />
 ));
 
 export const UrlPreviewImg = as<'img'>(({ className, alt, ...props }, ref) => (