fix(profile): 修复嵌套 Row 无界约束导致的白屏问题

在 _buildSettlementSection 的"已结算"区域，内层 Row 中使用了 Flexible，
但内层 Row 没有宽度约束，导致 RenderFlex unbounded width constraints 错误。
通过在内层 Row 外添加 Expanded 包裹来提供宽度约束。

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

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

frontend/mobile-app/lib/features/profile/presentation/pages/profile_page.dart

@@ -2475,35 +2475,37 @@ class _ProfilePageState extends ConsumerState<ProfilePage> {
           Row(
             mainAxisAlignment: MainAxisAlignment.spaceBetween,
             children: [
-              Row(
-                children: [
-                  const Text(
-                    '已结算 (绿积分)：',
-                    style: TextStyle(
-                      fontSize: 14,
-                      fontFamily: 'Inter',
-                      fontWeight: FontWeight.w500,
-                      height: 1.5,
-                      color: Color(0xCC5D4037),
+              Expanded(
+                child: Row(
+                  children: [
+                    const Text(
+                      '已结算 (绿积分)：',
+                      style: TextStyle(
+                        fontSize: 14,
+                        fontFamily: 'Inter',
+                        fontWeight: FontWeight.w500,
+                        height: 1.5,
+                        color: Color(0xCC5D4037),
+                      ),
                     ),
-                  ),
-                  Flexible(
-                    child: FittedBox(
-                      fit: BoxFit.scaleDown,
-                      alignment: Alignment.centerLeft,
-                      child: Text(
-                        _formatNumber(_settledUsdt),
-                        style: const TextStyle(
-                          fontSize: 14,
-                          fontFamily: 'Inter',
-                          fontWeight: FontWeight.w700,
-                          height: 1.5,
-                          color: Color(0xFF5D4037),
+                    Flexible(
+                      child: FittedBox(
+                        fit: BoxFit.scaleDown,
+                        alignment: Alignment.centerLeft,
+                        child: Text(
+                          _formatNumber(_settledUsdt),
+                          style: const TextStyle(
+                            fontSize: 14,
+                            fontFamily: 'Inter',
+                            fontWeight: FontWeight.w700,
+                            height: 1.5,
+                            color: Color(0xFF5D4037),
+                          ),
                         ),
                       ),
                     ),
-                  ),
-                ],
+                  ],
+                ),
               ),
               GestureDetector(
                 onTap: _onSettlement,