feat: format numbers >= billion with k suffix

- Update formatNumber function to display numbers >= 1 billion with 'k' suffix
- Example: 2,500,000,000 displays as '2,500,000k' for better readability
- Improves token statistics display for large numbers

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

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

web/admin/app.js

@@ -2488,7 +2488,11 @@ const app = createApp({
         // 格式化数字，添加千分符
         formatNumber(num) {
             if (num === null || num === undefined) return '0';
-            return Number(num).toLocaleString();
+            const number = Number(num);
+            if (number >= 1000000000) {
+                return (number / 1000).toLocaleString() + 'k';
+            }
+            return number.toLocaleString();
         },
 
         // 格式化运行时间