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/components/CompetitionPage.tsx

@@ -116,7 +116,7 @@ export function CompetitionPage() {
               {t('realTimePnL', language)}
             </div>
           </div>
-          <ComparisonChart traders={sortedTraders} />
+          <ComparisonChart traders={sortedTraders.slice(0, 5)} />
         </div>
 
         {/* Right: Leaderboard */}