feat(l10n): UI 텍스트 아스키나라 세계관 적용

app_en.arb / app_ko.arb:
- appTitle: "ASCII-Nara" / "아스키나라"
- progressQuestTitle: "ASCII-Nara - {name}"
- welcomeMessage: 아스키나라 환영 메시지

자동 생성 파일 업데이트:
- app_localizations.dart
- app_localizations_en.dart
- app_localizations_ko.dart

lib/l10n/app_localizations_en.dart

@@ -9,7 +9,7 @@ class L10nEn extends L10n {
   L10nEn([String locale = 'en']) : super(locale);
 
   @override
-  String get appTitle => 'Ascii Never Die';
+  String get appTitle => 'ASCII-Nara';
 
   @override
   String get tagNoNetwork => 'No network';
@@ -55,7 +55,7 @@ class L10nEn extends L10n {
 
   @override
   String progressQuestTitle(String name) {
-    return 'Progress Quest - $name';
+    return 'ASCII-Nara - $name';
   }
 
   @override
@@ -197,7 +197,7 @@ class L10nEn extends L10n {
   }
 
   @override
-  String get welcomeMessage => 'Welcome to Progress Quest!';
+  String get welcomeMessage => 'Welcome to ASCII-Nara!';
 
   @override
   String get noSavedGames => 'No saved games found.';