LineItem total: increase top padding for visual balance

mt/pt bumped from 1.5 (12px) to 2 (16px), add pb: 0.5 (4px) so
the text sits more centred between the border-top and the content below.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/molecules/LineItem/LineItem.tsx

@@ -61,8 +61,9 @@ export const LineItem = React.forwardRef<HTMLDivElement, LineItemProps>(
             justifyContent: 'space-between',
             gap: 2,
             ...(isTotal && {
-              pt: 1.5,
-              mt: 1.5,
+              pt: 2,
+              pb: 0.5,
+              mt: 2,
               borderTop: '1px solid',
               borderColor: 'divider',
             }),