fix(mobile): 简化火柴人位置计算逻辑

使用简单直接的比例计算：
- 起点 = 昵称区域右边 (70px)
- 终点 = 红旗左边 (containerWidth - 62px)
- 火柴人位置 = 起点 + (终点 - 起点) * 进度

🤖 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

@@ -183,159 +183,150 @@ class _StickmanRaceWidgetState extends State<StickmanRaceWidget>
 
     return SizedBox(
       height: raceTrackHeight,
-      child: Stack(
-        children: [
-          // 背景赛道线
-          Positioned.fill(
-            child: CustomPaint(
-              painter: _TrackPainter(
-                trackCount: sortedRankings.length,
-              ),
-            ),
-          ),
+      child: LayoutBuilder(
+        builder: (context, constraints) {
+          final containerWidth = constraints.maxWidth;
 
-          // 每个跑道的终点红旗
-          ...List.generate(trackCount, (index) {
-            final verticalPosition = index * trackHeight + 10 + trackHeight / 2 - 16;
-            return Positioned(
-              right: 8,
-              top: verticalPosition,
-              child: const Icon(
-                Icons.flag,
-                color: Colors.red,
-                size: 24,
+          return Stack(
+            clipBehavior: Clip.none,
+            children: [
+              // 背景赛道线
+              Positioned.fill(
+                child: CustomPaint(
+                  painter: _TrackPainter(
+                    trackCount: sortedRankings.length,
+                  ),
+                ),
               ),
-            );
-          }),
 
-          // 火柴人们
-          ...sortedRankings.asMap().entries.map((entry) {
-            final index = entry.key;
-            final data = entry.value;
-            return _buildStickman(data, index, sortedRankings.length, raceTrackHeight);
-          }),
-        ],
+              // 每个跑道的终点红旗
+              ...List.generate(trackCount, (index) {
+                final verticalPosition = index * trackHeight + 10 + trackHeight / 2 - 16;
+                return Positioned(
+                  right: 8,
+                  top: verticalPosition,
+                  child: const Icon(
+                    Icons.flag,
+                    color: Colors.red,
+                    size: 24,
+                  ),
+                );
+              }),
+
+              // 火柴人们
+              ...sortedRankings.asMap().entries.map((entry) {
+                final index = entry.key;
+                final data = entry.value;
+                return _buildStickman(data, index, sortedRankings.length, raceTrackHeight, containerWidth);
+              }),
+            ],
+          );
+        },
       ),
     );
   }
 
   /// 构建单个火柴人
-  Widget _buildStickman(StickmanRankingData data, int rank, int total, double raceTrackHeight) {
-    // 计算水平位置 (根据进度)
-    final horizontalProgress = data.progress;
+  Widget _buildStickman(StickmanRankingData data, int rank, int total, double raceTrackHeight, double containerWidth) {
+    // 进度 (0.0 - 1.0)
+    final progress = data.progress;
 
     // 计算垂直位置 (不同排名在不同跑道)
-    // 预留顶部和底部空间
     final usableHeight = raceTrackHeight - 40;
     final trackHeight = usableHeight / total;
     final verticalPosition = rank * trackHeight + 10;
 
+    // 简单直接的计算：
+    // 起点：昵称区域右边 (70)
+    // 终点：红旗左边 (containerWidth - 8(红旗right) - 24(红旗宽) - 30(火柴人半宽))
+    // 火柴人中心位置 = 起点 + (终点 - 起点) * 进度
+    const double startX = 70.0;
+    final double endX = containerWidth - 62.0;
+    final double stickmanCenterX = startX + (endX - startX) * progress;
+
     return AnimatedBuilder(
       animation: _bounceController,
       builder: (context, child) {
-        // 添加上下弹跳效果
         final bounce = _bounceController.value * 3;
 
-        // 计算可用宽度，让火柴人在100%时正好到达红旗位置
-        final screenWidth = MediaQuery.of(context).size.width;
-        final containerWidth = screenWidth - 32 - 32; // 页面padding + 容器padding
-        final stickmanColumnWidth = 60.0; // 火柴人+数量标签列的宽度
-        final flagRightMargin = 8.0; // 红旗的right值
-        final flagWidth = 24.0; // 红旗图标宽度
-        final nicknameAreaWidth = 65.0; // 昵称区域宽度
-        final gap = 4.0; // 昵称和火柴人之间的最小间距
-
-        // 100%时火柴人列的右边缘应该对齐红旗左边缘
-        // 红旗左边位置 = containerWidth - flagRightMargin - flagWidth
-        // 火柴人列右边 = stickmanLeftPosition + stickmanColumnWidth
-        // 所以 100% 时: stickmanLeftPosition = containerWidth - flagRightMargin - flagWidth - stickmanColumnWidth
-        final endPosition = containerWidth - flagRightMargin - flagWidth - stickmanColumnWidth;
-        final startPosition = nicknameAreaWidth + gap;
-        final availableWidth = endPosition - startPosition;
-        final stickmanLeftPosition = startPosition + availableWidth * horizontalProgress;
-
-        return Positioned(
-          left: 0,
-          top: verticalPosition - bounce,
-          child: SizedBox(
-            width: containerWidth,
-            child: Row(
-              crossAxisAlignment: CrossAxisAlignment.start,
-              children: [
-                // 昵称标签 - 固定在左边，与数量标签同一水平高度
-                SizedBox(
-                  width: nicknameAreaWidth,
-                  child: Container(
-                    padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
-                    decoration: BoxDecoration(
-                      color: data.isCurrentUser
-                          ? const Color(0xFFD4AF37).withValues(alpha: 0.2)
-                          : Colors.white.withValues(alpha: 0.8),
-                      borderRadius: BorderRadius.circular(8),
-                      border: data.isCurrentUser
-                          ? Border.all(color: const Color(0xFFD4AF37), width: 1)
-                          : null,
-                    ),
-                    child: Text(
-                      data.nickname,
-                      style: TextStyle(
-                        fontSize: 9,
-                        fontFamily: 'Inter',
-                        fontWeight:
-                            data.isCurrentUser ? FontWeight.w600 : FontWeight.w400,
-                        color: data.isCurrentUser
-                            ? const Color(0xFFD4AF37)
-                            : const Color(0xFF5D4037),
-                      ),
-                      overflow: TextOverflow.ellipsis,
-                      textAlign: TextAlign.center,
-                    ),
+        return Stack(
+          clipBehavior: Clip.none,
+          children: [
+            // 昵称标签 - 固定在左边
+            Positioned(
+              left: 0,
+              top: verticalPosition + 15 - bounce,
+              child: SizedBox(
+                width: 65,
+                child: Container(
+                  padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
+                  decoration: BoxDecoration(
+                    color: data.isCurrentUser
+                        ? const Color(0xFFD4AF37).withValues(alpha: 0.2)
+                        : Colors.white.withValues(alpha: 0.8),
+                    borderRadius: BorderRadius.circular(8),
+                    border: data.isCurrentUser
+                        ? Border.all(color: const Color(0xFFD4AF37), width: 1)
+                        : null,
                   ),
-                ),
-                // 间隔 + 火柴人位置
-                SizedBox(
-                  width: stickmanLeftPosition - nicknameAreaWidth,
-                ),
-                // 火柴人和数量标签
-                Column(
-                  mainAxisSize: MainAxisSize.min,
-                  children: [
-                    // 完成数量标签
-                    Container(
-                      constraints: const BoxConstraints(maxWidth: 60),
-                      padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
-                      decoration: BoxDecoration(
-                        color: data.isCurrentUser
-                            ? const Color(0xFFD4AF37)
-                            : const Color(0xFF8B5A2B),
-                        borderRadius: BorderRadius.circular(8),
-                      ),
-                      child: FittedBox(
-                        fit: BoxFit.scaleDown,
-                        child: Text(
-                          '${_formatNumber(data.completedCount)}棵',
-                          style: const TextStyle(
-                            fontSize: 9,
-                            fontFamily: 'Inter',
-                            fontWeight: FontWeight.w600,
-                            color: Colors.white,
-                          ),
-                        ),
-                      ),
-                    ),
-                    const SizedBox(height: 2),
-                    // 火柴人动画
-                    RunningStickman(
-                      size: 36,
+                  child: Text(
+                    data.nickname,
+                    style: TextStyle(
+                      fontSize: 9,
+                      fontFamily: 'Inter',
+                      fontWeight: data.isCurrentUser ? FontWeight.w600 : FontWeight.w400,
                       color: data.isCurrentUser
                           ? const Color(0xFFD4AF37)
                           : const Color(0xFF5D4037),
                     ),
-                  ],
+                    overflow: TextOverflow.ellipsis,
+                    textAlign: TextAlign.center,
+                  ),
                 ),
-              ],
+              ),
             ),
-          ),
+            // 火柴人和数量标签
+            Positioned(
+              left: stickmanCenterX - 30,  // 火柴人宽度60的一半
+              top: verticalPosition - bounce,
+              child: Column(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  // 完成数量标签
+                  Container(
+                    constraints: const BoxConstraints(maxWidth: 60),
+                    padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                    decoration: BoxDecoration(
+                      color: data.isCurrentUser
+                          ? const Color(0xFFD4AF37)
+                          : const Color(0xFF8B5A2B),
+                      borderRadius: BorderRadius.circular(8),
+                    ),
+                    child: FittedBox(
+                      fit: BoxFit.scaleDown,
+                      child: Text(
+                        '${_formatNumber(data.completedCount)}棵',
+                        style: const TextStyle(
+                          fontSize: 9,
+                          fontFamily: 'Inter',
+                          fontWeight: FontWeight.w600,
+                          color: Colors.white,
+                        ),
+                      ),
+                    ),
+                  ),
+                  const SizedBox(height: 2),
+                  // 火柴人动画
+                  RunningStickman(
+                    size: 36,
+                    color: data.isCurrentUser
+                        ? const Color(0xFFD4AF37)
+                        : const Color(0xFF5D4037),
+                  ),
+                ],
+              ),
+            ),
+          ],
         );
       },
     );