feat(trading): enable one-click settlement button

开放兑换页面的"一键结算"功能：

- 有可结算收益时：显示"一键结算"，按钮可点击（金色）
- 无可结算收益时：显示"暂无可结算收益"，按钮禁用（半透明）
- 结算中：显示加载动画，防止重复点击
- 使用 rewardService.settleToBalance() API 执行结算
- 结算成功后自动刷新页面数据

🤖 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

@@ -93,7 +93,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
       builder: (context) => AlertDialog(
         title: const Text('确认结算'),
         content: Text(
-          '确定将 ${_formatNumber(_settleableAmount)} 绿积分 结算为 ${_getCurrencyName(_selectedCurrency)} 吗？',
+          '确定将 ${_formatNumber(_settleableAmount)} 绿积分 结算到钱包余额吗？',
         ),
         actions: [
           TextButton(
@@ -122,26 +122,27 @@ class _TradingPageState extends ConsumerState<TradingPage> {
 
     try {
       debugPrint('[TradingPage] 开始结算...');
-      debugPrint('[TradingPage]   金额: $_settleableAmount USDT');
-      debugPrint('[TradingPage]   币种: ${_getCurrencyName(_selectedCurrency)}');
+      debugPrint('[TradingPage]   金额: $_settleableAmount 绿积分');
 
-      final walletService = ref.read(walletServiceProvider);
-      final orderId = await walletService.settleRewards(
-        usdtAmount: _settleableAmount,
-        settleCurrency: _getCurrencyName(_selectedCurrency),
-      );
+      // 使用 reward-service 的 settleToBalance API
+      final rewardService = ref.read(rewardServiceProvider);
+      final result = await rewardService.settleToBalance();
 
-      debugPrint('[TradingPage] 结算成功: orderId=$orderId');
+      if (result.success) {
+        debugPrint('[TradingPage] 结算成功: settlementId=${result.settlementId}, amount=${result.settledUsdtAmount}');
 
-      if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(
-            content: Text('结算成功'),
-            backgroundColor: Color(0xFFD4AF37),
-          ),
-        );
-        // 刷新钱包数据
-        _loadWalletData();
+        if (mounted) {
+          ScaffoldMessenger.of(context).showSnackBar(
+            SnackBar(
+              content: Text('结算成功，${result.settledUsdtAmount.toStringAsFixed(2)} 绿积分已转入钱包余额'),
+              backgroundColor: const Color(0xFFD4AF37),
+            ),
+          );
+          // 刷新钱包数据
+          _loadWalletData();
+        }
+      } else {
+        throw Exception(result.error ?? '结算失败');
       }
     } catch (e) {
       debugPrint('[TradingPage] 结算失败: $e');
@@ -371,33 +372,44 @@ class _TradingPageState extends ConsumerState<TradingPage> {
   }
 
   /// 构建一键结算按钮
-  /// 注意：一键结算功能暂时禁用
   Widget _buildSettlementButton() {
-    // 功能暂时禁用，始终不可点击
-    const bool canSettle = false;
+    // 根据可结算金额判断是否可点击
+    final bool canSettle = _settleableAmount > 0 && !_isSettling;
+
     return Padding(
       padding: const EdgeInsets.symmetric(horizontal: 16),
       child: GestureDetector(
-        onTap: null, // 功能暂时禁用
+        onTap: canSettle ? _onSettlement : null,
         child: Container(
           width: double.infinity,
           height: 56,
           decoration: BoxDecoration(
-            color: const Color(0x80D4AF37), // 禁用状态颜色
+            color: canSettle
+                ? const Color(0xFFD4AF37)  // 启用状态：金色
+                : const Color(0x80D4AF37), // 禁用状态：半透明金色
             borderRadius: BorderRadius.circular(12),
           ),
-          child: const Center(
-            child: Text(
-              '一键结算（暂未开放）',
-              style: TextStyle(
-                fontSize: 16,
-                fontFamily: 'Inter',
-                fontWeight: FontWeight.w700,
-                height: 1.5,
-                letterSpacing: 0.24,
-                color: Colors.white,
-              ),
-            ),
+          child: Center(
+            child: _isSettling
+                ? const SizedBox(
+                    width: 24,
+                    height: 24,
+                    child: CircularProgressIndicator(
+                      strokeWidth: 2,
+                      color: Colors.white,
+                    ),
+                  )
+                : Text(
+                    canSettle ? '一键结算' : '暂无可结算收益',
+                    style: const TextStyle(
+                      fontSize: 16,
+                      fontFamily: 'Inter',
+                      fontWeight: FontWeight.w700,
+                      height: 1.5,
+                      letterSpacing: 0.24,
+                      color: Colors.white,
+                    ),
+                  ),
           ),
         ),
       ),