feat(l10n): 국제화(L10n) 시스템 도입 및 하드코딩 텍스트 변환

- flutter_localizations 및 intl 패키지 추가
- l10n.yaml 설정 파일 및 app_ko.arb 메시지 파일 생성
- 모든 화면(app, front, game_play, new_character, save_picker)의 하드코딩 텍스트를 L10n 키로 변환
- 테스트 파일에 localizationsDelegates 추가하여 L10n 지원

lib/src/features/new_character/new_character_screen.dart

@@ -2,6 +2,7 @@ import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
 
+import 'package:askiineverdie/l10n/app_localizations.dart';
 import 'package:askiineverdie/src/core/model/game_state.dart';
 import 'package:askiineverdie/src/core/model/pq_config.dart';
 import 'package:askiineverdie/src/core/util/deterministic_random.dart';
@@ -241,6 +242,7 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
   }
 
   Widget _buildNameSection() {
+    final l10n = L10n.of(context);
     return Card(
       child: Padding(
         padding: const EdgeInsets.all(16),
@@ -249,9 +251,9 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
             Expanded(
               child: TextField(
                 controller: _nameController,
-                decoration: const InputDecoration(
-                  labelText: 'Name',
-                  border: OutlineInputBorder(),
+                decoration: InputDecoration(
+                  labelText: l10n.name,
+                  border: const OutlineInputBorder(),
                 ),
                 maxLength: 30,
               ),
@@ -260,7 +262,7 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
             IconButton.filled(
               onPressed: _onGenerateName,
               icon: const Icon(Icons.casino),
-              tooltip: 'Generate Name',
+              tooltip: l10n.generateName,
             ),
           ],
         ),
@@ -269,29 +271,30 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
   }
 
   Widget _buildStatsSection() {
+    final l10n = L10n.of(context);
     return Card(
       child: Padding(
         padding: const EdgeInsets.all(16),
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
-            Text('Stats', style: Theme.of(context).textTheme.titleMedium),
+            Text(l10n.stats, style: Theme.of(context).textTheme.titleMedium),
             const SizedBox(height: 12),
 
             // 스탯 그리드
             Row(
               children: [
-                Expanded(child: _buildStatTile('STR', _str)),
-                Expanded(child: _buildStatTile('CON', _con)),
-                Expanded(child: _buildStatTile('DEX', _dex)),
+                Expanded(child: _buildStatTile(l10n.statStr, _str)),
+                Expanded(child: _buildStatTile(l10n.statCon, _con)),
+                Expanded(child: _buildStatTile(l10n.statDex, _dex)),
               ],
             ),
             const SizedBox(height: 8),
             Row(
               children: [
-                Expanded(child: _buildStatTile('INT', _int)),
-                Expanded(child: _buildStatTile('WIS', _wis)),
-                Expanded(child: _buildStatTile('CHA', _cha)),
+                Expanded(child: _buildStatTile(l10n.statInt, _int)),
+                Expanded(child: _buildStatTile(l10n.statWis, _wis)),
+                Expanded(child: _buildStatTile(l10n.statCha, _cha)),
               ],
             ),
             const SizedBox(height: 12),
@@ -307,9 +310,9 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
               child: Row(
                 mainAxisAlignment: MainAxisAlignment.spaceBetween,
                 children: [
-                  const Text(
-                    'Total',
-                    style: TextStyle(fontWeight: FontWeight.bold),
+                  Text(
+                    l10n.total,
+                    style: const TextStyle(fontWeight: FontWeight.bold),
                   ),
                   Text(
                     '$_total',
@@ -333,7 +336,7 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
                 OutlinedButton.icon(
                   onPressed: _onUnroll,
                   icon: const Icon(Icons.undo),
-                  label: const Text('Unroll'),
+                  label: Text(l10n.unroll),
                   style: OutlinedButton.styleFrom(
                     foregroundColor: _rollHistory.isEmpty ? Colors.grey : null,
                   ),
@@ -342,7 +345,7 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
                 FilledButton.icon(
                   onPressed: _onReroll,
                   icon: const Icon(Icons.casino),
-                  label: const Text('Roll'),
+                  label: Text(l10n.roll),
                 ),
               ],
             ),
@@ -389,7 +392,7 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
-            Text('Race', style: Theme.of(context).textTheme.titleMedium),
+            Text(L10n.of(context).race, style: Theme.of(context).textTheme.titleMedium),
             const SizedBox(height: 8),
             SizedBox(
               height: 300,
@@ -434,7 +437,7 @@ class _NewCharacterScreenState extends State<NewCharacterScreen> {
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
-            Text('Class', style: Theme.of(context).textTheme.titleMedium),
+            Text(L10n.of(context).classTitle, style: Theme.of(context).textTheme.titleMedium),
             const SizedBox(height: 8),
             SizedBox(
               height: 300,