fix(mobile-app): 修复火柴人组件宽度和行间隔问题

1. 将水平边距从16改为20，与其他组件一致
2. 根据火柴人数量动态计算赛道高度，每个火柴人85px
3. 避免火柴人数量标签覆盖到其他火柴人

🤖 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

@@ -83,7 +83,7 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
     }
 
     return Container(
-      margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
+      margin: const EdgeInsets.symmetric(horizontal: 20, vertical: 8),
       padding: const EdgeInsets.all(16),
       decoration: BoxDecoration(
         color: const Color(0x80FFFFFF),
@@ -159,14 +159,21 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
     );
   }
 
+  /// 每个火柴人需要的最小高度（标签+动画+昵称）
+  static const double _minTrackHeight = 85.0;
+
   /// 构建赛道区域
   Widget _buildRaceTrack() {
     // 按完成数量排序
     final sortedRankings = List<StickmanRankingData>.from(widget.rankings)
       ..sort((a, b) => b.completedCount.compareTo(a.completedCount));
 
+    // 根据火柴人数量动态计算赛道高度
+    final trackCount = sortedRankings.length;
+    final raceTrackHeight = (trackCount * _minTrackHeight).clamp(160.0, 500.0);
+
     return SizedBox(
-      height: 160,
+      height: raceTrackHeight,
       child: Stack(
         children: [
           // 背景赛道线
@@ -208,7 +215,7 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
           ...sortedRankings.asMap().entries.map((entry) {
             final index = entry.key;
             final data = entry.value;
-            return _buildStickman(data, index, sortedRankings.length);
+            return _buildStickman(data, index, sortedRankings.length, raceTrackHeight);
           }),
         ],
       ),
@@ -216,12 +223,14 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
   }
 
   /// 构建单个火柴人
-  Widget _buildStickman(StickmanRankingData data, int rank, int total) {
+  Widget _buildStickman(StickmanRankingData data, int rank, int total, double raceTrackHeight) {
     // 计算水平位置 (根据进度)
     final horizontalProgress = data.progress;
 
     // 计算垂直位置 (不同排名在不同跑道)
-    final trackHeight = 120.0 / total;
+    // 预留顶部和底部空间
+    final usableHeight = raceTrackHeight - 40;
+    final trackHeight = usableHeight / total;
     final verticalPosition = rank * trackHeight + 10;
 
     return AnimatedBuilder(