feat(ui): 반응형 레이아웃 및 저장 시스템 개선

## 반응형 레이아웃
- app.dart: 화면 크기별 레이아웃 분기 로직 추가 (+173 라인)
- game_play_screen.dart: 반응형 UI 구조 개선
- layouts/, pages/ 디렉토리 추가 (새 레이아웃 시스템)
- carousel_nav_bar.dart: 캐러셀 네비게이션 바 추가
- enhanced_animation_panel.dart: 향상된 애니메이션 패널

## 저장 시스템
- save_manager.dart: 저장 관리 기능 확장
- save_repository.dart: 저장소 인터페이스 개선
- save_service.dart: 저장 서비스 로직 추가

## UI 개선
- notification_service.dart: 알림 시스템 기능 확장
- notification_overlay.dart: 오버레이 UI 개선
- equipment_stats_panel.dart: 장비 스탯 패널 개선
- cinematic_view.dart: 시네마틱 뷰 개선
- new_character_screen.dart: 캐릭터 생성 화면 개선

## 다국어
- game_text_l10n.dart: 텍스트 추가 (+182 라인)

## 테스트
- 관련 테스트 파일 업데이트

lib/src/features/game/pages/character_sheet_page.dart

@@ -0,0 +1,133 @@
+import 'package:flutter/material.dart';
+
+import 'package:askiineverdie/l10n/app_localizations.dart';
+import 'package:askiineverdie/src/core/l10n/game_data_l10n.dart';
+import 'package:askiineverdie/src/core/model/game_state.dart';
+import 'package:askiineverdie/src/features/game/widgets/stats_panel.dart';
+
+/// 캐릭터시트 페이지 (캐로셀 - 기본 페이지)
+///
+/// 트레잇, 스탯, 경험치 표시.
+class CharacterSheetPage extends StatelessWidget {
+  const CharacterSheetPage({
+    super.key,
+    required this.traits,
+    required this.stats,
+    required this.exp,
+  });
+
+  final Traits traits;
+  final Stats stats;
+  final ProgressBarState exp;
+
+  @override
+  Widget build(BuildContext context) {
+    final localizations = L10n.of(context);
+
+    return SingleChildScrollView(
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        children: [
+          // 트레잇
+          _buildSectionHeader(context, localizations.traits),
+          _buildTraitsList(context),
+
+          // 스탯
+          _buildSectionHeader(context, localizations.stats),
+          StatsPanel(stats: stats),
+
+          // 경험치
+          _buildSectionHeader(context, localizations.experience),
+          _buildExpBar(context),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildSectionHeader(BuildContext context, String title) {
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+      color: Theme.of(context).colorScheme.primaryContainer,
+      child: Text(
+        title,
+        style: TextStyle(
+          fontWeight: FontWeight.bold,
+          fontSize: 13,
+          color: Theme.of(context).colorScheme.onPrimaryContainer,
+        ),
+      ),
+    );
+  }
+
+  Widget _buildTraitsList(BuildContext context) {
+    final localizations = L10n.of(context);
+    final traitData = [
+      (localizations.traitName, traits.name),
+      (localizations.traitRace, GameDataL10n.getRaceName(context, traits.race)),
+      (
+        localizations.traitClass,
+        GameDataL10n.getKlassName(context, traits.klass),
+      ),
+      (localizations.traitLevel, '${traits.level}'),
+    ];
+
+    return Padding(
+      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
+      child: Column(
+        children: traitData.map((t) {
+          return Padding(
+            padding: const EdgeInsets.symmetric(vertical: 2),
+            child: Row(
+              children: [
+                SizedBox(
+                  width: 60,
+                  child: Text(
+                    t.$1,
+                    style: TextStyle(fontSize: 12, color: Colors.grey.shade600),
+                  ),
+                ),
+                Expanded(
+                  child: Text(
+                    t.$2,
+                    style: const TextStyle(
+                      fontSize: 13,
+                      fontWeight: FontWeight.bold,
+                    ),
+                    overflow: TextOverflow.ellipsis,
+                  ),
+                ),
+              ],
+            ),
+          );
+        }).toList(),
+      ),
+    );
+  }
+
+  Widget _buildExpBar(BuildContext context) {
+    final localizations = L10n.of(context);
+    final progress = exp.max > 0
+        ? (exp.position / exp.max).clamp(0.0, 1.0)
+        : 0.0;
+    final remaining = exp.max - exp.position;
+
+    return Padding(
+      padding: const EdgeInsets.all(12),
+      child: Column(
+        children: [
+          LinearProgressIndicator(
+            value: progress,
+            backgroundColor: Colors.blue.withValues(alpha: 0.2),
+            valueColor: const AlwaysStoppedAnimation<Color>(Colors.blue),
+            minHeight: 12,
+          ),
+          const SizedBox(height: 4),
+          Text(
+            '$remaining ${localizations.xpNeededForNextLevel}',
+            style: TextStyle(fontSize: 10, color: Colors.grey.shade600),
+          ),
+        ],
+      ),
+    );
+  }
+}