style: dart format 적용

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

lib/src/features/game/game_play_screen.dart

@@ -714,7 +714,10 @@ class _GamePlayScreenState extends State<GamePlayScreen>
   }
 
   /// 데스크톱 앱바
-  PreferredSizeWidget _buildDesktopAppBar(BuildContext context, GameState state) {
+  PreferredSizeWidget _buildDesktopAppBar(
+    BuildContext context,
+    GameState state,
+  ) {
     return AppBar(
       backgroundColor: RetroColors.darkBrown,
       title: Text(
@@ -969,9 +972,7 @@ class _GamePlayScreenState extends State<GamePlayScreen>
           // Potions (물약 인벤토리)
           _buildSectionHeader(game_l10n.uiPotions),
           Expanded(
-            child: PotionInventoryPanel(
-              inventory: state.potionInventory,
-            ),
+            child: PotionInventoryPanel(inventory: state.potionInventory),
           ),
 
           // Encumbrance 바