fix(ui): 修复分割线透明度问题

- 使用 ghostBorder 替代 outlineVariant.withAlpha(0.1)
- 提高分割线可见度

flutter_monisuo/lib/ui/pages/home/home_page.dart

@@ -1038,7 +1038,7 @@ class _HoldingsList extends StatelessWidget {
         padding: EdgeInsets.all(AppSpacing.md),
         itemCount: displayHoldings.length,
         separatorBuilder: (_, __) => Divider(
-          color: context.colors.outlineVariant.withValues(alpha: 0.1),
+          color: context.appColors.ghostBorder,
           height: 1,
         ),
         itemBuilder: (context, index) =>