fix(mobile-app): 修复火柴人容器宽度与其他组件不一致

- 移除火柴人容器的水平margin，与页面其他内容保持一致
- 重新计算火柴人位置，正确处理容器边距

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

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

frontend/mobile-app/lib/features/authorization/presentation/widgets/stickman_race_widget.dart

@@ -82,7 +82,7 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
     }
 
     return Container(
-      margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
+      margin: const EdgeInsets.only(bottom: 16),
       padding: const EdgeInsets.all(16),
       decoration: BoxDecoration(
         color: const Color(0x80FFFFFF),
@@ -238,13 +238,14 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
         // 添加上下弹跳效果
         final bounce = _bounceController.value * 3;
 
-        // 计算可用宽度：容器宽度 - 左边距(20) - 右边距(终点区域80) - 火柴人宽度(60)
-        final containerWidth = MediaQuery.of(context).size.width - 32; // 减去容器外边距
-        final availableWidth = containerWidth - 20 - 80 - 60; // 起点边距 - 终点区域 - 火柴人宽度
-        final leftPosition = 20 + availableWidth * horizontalProgress;
+        // 计算可用宽度：屏幕宽度 - 页面padding(32) - 容器padding(32) - 终点区域(60) - 火柴人宽度(60)
+        final screenWidth = MediaQuery.of(context).size.width;
+        final containerWidth = screenWidth - 32 - 32; // 页面padding + 容器padding
+        final availableWidth = containerWidth - 60 - 60; // 终点区域 - 火柴人宽度
+        final leftPosition = availableWidth * horizontalProgress;
 
         return Positioned(
-          left: leftPosition.clamp(20.0, containerWidth - 80), // 确保不超出右边界
+          left: leftPosition.clamp(0.0, availableWidth), // 确保不超出右边界
           top: verticalPosition - bounce,
           child: Column(
             mainAxisSize: MainAxisSize.min,