fix(trading): 将提取/转动按钮下的人民币改为积分

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mobile-app/lib/features/trading/presentation/pages/trading_page.dart

@@ -592,7 +592,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
             ),
           )
         : Text(
-            '人民币 余额: ${_formatNumber(_usdtBalance)}',
+            '积分 余额: ${_formatNumber(_usdtBalance)}',
             style: const TextStyle(
               fontSize: 14,
               fontFamily: 'Inter',