feat(ui): 화면들에 레트로 UI 스타일 적용

- front_screen: 레트로 패널 및 버튼 스타일
- game_play_screen: 레트로 색상 및 초기 BGM 로직 개선
- mobile_carousel_layout: 레트로 테마 적용
- carousel_nav_bar: 골드 액센트 색상 적용

lib/src/features/game/game_play_screen.dart

@@ -36,6 +36,7 @@ import 'package:askiineverdie/src/features/game/widgets/statistics_dialog.dart';
 import 'package:askiineverdie/src/features/game/widgets/help_dialog.dart';
 import 'package:askiineverdie/src/core/storage/settings_repository.dart';
 import 'package:askiineverdie/src/core/audio/audio_service.dart';
+import 'package:askiineverdie/src/shared/retro_colors.dart';
 
 /// 게임 진행 화면 (Main.dfm 기반 3패널 레이아웃)
 ///
@@ -829,7 +830,7 @@ class _GamePlayScreenState extends State<GamePlayScreen>
       );
     }
 
-    // 기존 데스크톱 레이아웃
+    // 기존 데스크톱 레이아웃 (레트로 스타일)
     return NotificationOverlay(
       key: localeKey,
       notificationService: _notificationService,
@@ -846,8 +847,17 @@ class _GamePlayScreenState extends State<GamePlayScreen>
           }
         },
         child: Scaffold(
+          backgroundColor: RetroColors.deepBrown,
           appBar: AppBar(
-            title: Text(L10n.of(context).progressQuestTitle(state.traits.name)),
+            backgroundColor: RetroColors.darkBrown,
+            title: Text(
+              L10n.of(context).progressQuestTitle(state.traits.name),
+              style: const TextStyle(
+                fontFamily: 'PressStart2P',
+                fontSize: 12,
+                color: RetroColors.gold,
+              ),
+            ),
             actions: [
               // 치트 버튼 (디버그용)
               if (widget.controller.cheatsEnabled) ...[
@@ -955,6 +965,11 @@ class _GamePlayScreenState extends State<GamePlayScreen>
     final l10n = L10n.of(context);
     return Card(
       margin: const EdgeInsets.all(4),
+      color: RetroColors.panelBg,
+      shape: RoundedRectangleBorder(
+        side: const BorderSide(color: RetroColors.panelBorderOuter, width: 2),
+        borderRadius: BorderRadius.circular(0),
+      ),
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [
@@ -1023,6 +1038,11 @@ class _GamePlayScreenState extends State<GamePlayScreen>
     final l10n = L10n.of(context);
     return Card(
       margin: const EdgeInsets.all(4),
+      color: RetroColors.panelBg,
+      shape: RoundedRectangleBorder(
+        side: const BorderSide(color: RetroColors.panelBorderOuter, width: 2),
+        borderRadius: BorderRadius.circular(0),
+      ),
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [
@@ -1069,6 +1089,11 @@ class _GamePlayScreenState extends State<GamePlayScreen>
     final l10n = L10n.of(context);
     return Card(
       margin: const EdgeInsets.all(4),
+      color: RetroColors.panelBg,
+      shape: RoundedRectangleBorder(
+        side: const BorderSide(color: RetroColors.panelBorderOuter, width: 2),
+        borderRadius: BorderRadius.circular(0),
+      ),
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [
@@ -1112,13 +1137,20 @@ class _GamePlayScreenState extends State<GamePlayScreen>
 
   Widget _buildPanelHeader(String title) {
     return Container(
-      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
-      color: Theme.of(context).colorScheme.primaryContainer,
+      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
+      decoration: const BoxDecoration(
+        color: RetroColors.darkBrown,
+        border: Border(
+          bottom: BorderSide(color: RetroColors.gold, width: 2),
+        ),
+      ),
       child: Text(
-        title,
-        style: TextStyle(
+        title.toUpperCase(),
+        style: const TextStyle(
+          fontFamily: 'PressStart2P',
+          fontSize: 8,
           fontWeight: FontWeight.bold,
-          color: Theme.of(context).colorScheme.onPrimaryContainer,
+          color: RetroColors.gold,
         ),
       ),
     );
@@ -1126,8 +1158,15 @@ class _GamePlayScreenState extends State<GamePlayScreen>
 
   Widget _buildSectionHeader(String title) {
     return Padding(
-      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
-      child: Text(title, style: Theme.of(context).textTheme.labelSmall),
+      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
+      child: Text(
+        title.toUpperCase(),
+        style: const TextStyle(
+          fontFamily: 'PressStart2P',
+          fontSize: 6,
+          color: RetroColors.textDisabled,
+        ),
+      ),
     );
   }