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.dart

@@ -104,7 +104,7 @@ abstract class L10n {
   /// Application title
   ///
   /// In en, this message translates to:
-  /// **'Ascii Never Die'**
+  /// **'ASCII-Nara'**
   String get appTitle;
 
   /// Tag indicating offline mode
@@ -194,7 +194,7 @@ abstract class L10n {
   /// Game screen title with character name
   ///
   /// In en, this message translates to:
-  /// **'Progress Quest - {name}'**
+  /// **'ASCII-Nara - {name}'**
   String progressQuestTitle(String name);
 
   /// Level up tooltip
@@ -464,7 +464,7 @@ abstract class L10n {
   /// Welcome message in task progress panel
   ///
   /// In en, this message translates to:
-  /// **'Welcome to Progress Quest!'**
+  /// **'Welcome to ASCII-Nara!'**
   String get welcomeMessage;
 
   /// No saved games message