Limit performance comparison chart to top 5 traders

Frontend changes to ensure equity-history-batch API only requests data for top 5 performers:
- Modify CompetitionPage to pass only top 5 traders to ComparisonChart component
- Update API comments to reflect the change from top 10 to top 5
- Optimize chart performance by reducing data volume and API calls

This ensures the performance comparison chart shows only the most relevant traders while improving load times.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: tinkle-community <tinklefund@gmail.com>

web/src/lib/api.ts

@@ -260,10 +260,10 @@ export const api = {
     return res.json();
   },
 
-  // 获取前10名交易员数据（无需认证）
+  // 获取前5名交易员数据（无需认证）
   async getTopTraders(): Promise<any[]> {
     const res = await fetch(`${API_BASE}/top-traders`);
-    if (!res.ok) throw new Error('获取前10名交易员失败');
+    if (!res.ok) throw new Error('获取前5名交易员失败');
     return res.json();
   },