feat: 移动端UI精致化优化

- 添加页面过渡动画（淡入+滑动）
- 优化统计卡片视觉，添加渐变色和微动效
- 实现列表项左滑删除手势（编辑+删除按钮）
- 优化底部导航，缩小高度并添加点击波纹效果
- 改进空状态，添加插画和引导按钮

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/components/EmptyState.js

@@ -0,0 +1,27 @@
+import { Icon } from './icons';
+
+export default function EmptyState({
+  icon = 'info',
+  title = '暂无数据',
+  description = '这里还没有内容',
+  action,
+  actionLabel,
+  onAction,
+}) {
+  return (
+    <div className="empty-state-enhanced">
+      <div className="empty-state-illustration">
+        <div className="empty-state-bg">
+          <Icon name={icon} size={32} />
+        </div>
+      </div>
+      <h3 className="empty-state-title">{title}</h3>
+      {description && <p className="empty-state-description">{description}</p>}
+      {action && (
+        <button type="button" className="btn btn-primary empty-state-action" onClick={onAction}>
+          {actionLabel}
+        </button>
+      )}
+    </div>
+  );
+}