20260607
优化 Vocabulary Library 的移动端体验：
- 精简移动端界面，隐藏重复标题、统计信息和多余筛选项
- 移动端只保留搜索功能
- 优化词本切换栏，自适应宽度并支持横向滚动
- 改善移动端大词库的滚动和加载体验
桌面端布局和功能保持不变。
20260607
Improved the Vocabulary Library experience on mobile:
- Simplified the mobile UI by hiding duplicate titles, stats, and extra filters
- Kept search as the primary mobile control
- Improved responsive vocabulary book tabs with horizontal scrolling
- Improved scrolling and loading behavior for large libraries on mobile
Desktop layout and controls remain unchanged.