style: dart format 적용

- 전체 Dart 소스 및 테스트 파일 포매팅 통일
- trailing comma, 줄바꿈, 인덴트 정리

lib/src/features/game/widgets/speed_boost_button.dart

@@ -65,10 +65,7 @@ class SpeedBoostButton extends StatelessWidget {
           Row(
             mainAxisSize: MainAxisSize.min,
             children: [
-              Text(
-                '⚡',
-                style: TextStyle(fontSize: 18, color: expColor),
-              ),
+              Text('⚡', style: TextStyle(fontSize: 18, color: expColor)),
               const SizedBox(width: 4),
               Text(
                 '${boostMultiplier}x',
@@ -113,10 +110,7 @@ class SpeedBoostButton extends StatelessWidget {
         child: Row(
           mainAxisSize: MainAxisSize.min,
           children: [
-            Text(
-              '⚡',
-              style: TextStyle(fontSize: 18, color: gold),
-            ),
+            Text('⚡', style: TextStyle(fontSize: 18, color: gold)),
             const SizedBox(width: 4),
             Text(
               '${boostMultiplier}x',
@@ -130,10 +124,7 @@ class SpeedBoostButton extends StatelessWidget {
             if (!isPaidUser) ...[
               const SizedBox(width: 6),
               Container(
-                padding: const EdgeInsets.symmetric(
-                  horizontal: 4,
-                  vertical: 2,
-                ),
+                padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
                 decoration: BoxDecoration(
                   color: Colors.white.withValues(alpha: 0.2),
                   borderRadius: BorderRadius.circular(4),