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/layouts/mobile_carousel_layout.dart

@@ -15,6 +15,7 @@ import 'package:askiineverdie/src/features/game/pages/story_page.dart';
 import 'package:askiineverdie/src/features/game/widgets/carousel_nav_bar.dart';
 import 'package:askiineverdie/src/features/game/widgets/combat_log.dart';
 import 'package:askiineverdie/src/features/game/widgets/enhanced_animation_panel.dart';
+import 'package:askiineverdie/src/shared/retro_colors.dart';
 
 /// 모바일 캐로셀 레이아웃
 ///
@@ -358,6 +359,7 @@ class _MobileCarouselLayoutState extends State<MobileCarouselLayout> {
     showModalBottomSheet<void>(
       context: context,
       isScrollControlled: true,
+      backgroundColor: RetroColors.panelBg,
       constraints: BoxConstraints(
         maxHeight: MediaQuery.of(context).size.height * 0.7,
       ),
@@ -366,19 +368,22 @@ class _MobileCarouselLayoutState extends State<MobileCarouselLayout> {
           child: Column(
             mainAxisSize: MainAxisSize.min,
             children: [
-            // 헤더
+            // 헤더 (레트로 스타일)
             Container(
               padding: const EdgeInsets.all(16),
               width: double.infinity,
-              decoration: BoxDecoration(
-                color: Theme.of(context).colorScheme.primaryContainer,
+              decoration: const BoxDecoration(
+                color: RetroColors.darkBrown,
+                border: Border(
+                  bottom: BorderSide(color: RetroColors.gold, width: 2),
+                ),
               ),
-              child: Text(
-                l10n.menuOptions,
+              child: const Text(
+                'OPTIONS',
                 style: TextStyle(
-                  fontWeight: FontWeight.bold,
-                  fontSize: 16,
-                  color: Theme.of(context).colorScheme.onPrimaryContainer,
+                  fontFamily: 'PressStart2P',
+                  fontSize: 12,
+                  color: RetroColors.gold,
                 ),
               ),
             ),
@@ -555,12 +560,21 @@ class _MobileCarouselLayoutState extends State<MobileCarouselLayout> {
     final state = widget.state;
 
     return 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: 10,
+            color: RetroColors.gold,
+          ),
+        ),
         actions: [
           // 옵션 버튼
           IconButton(
-            icon: const Icon(Icons.settings),
+            icon: const Icon(Icons.settings, color: RetroColors.gold),
             onPressed: () => _showOptionsMenu(context),
             tooltip: l10n.menuOptions,
           ),