refactor(l10n): 골드를 코인으로 명칭 변경

- gold → coin으로 용어 통일
- 사망 오버레이 레이블 수정

lib/l10n/app_localizations.dart

@@ -431,16 +431,16 @@ abstract class L10n {
   /// **'Sollerets'**
   String get equipSollerets;
 
-  /// Gold label
+  /// Coin label
   ///
   /// In en, this message translates to:
-  /// **'Gold'**
+  /// **'Coin'**
   String get gold;
 
-  /// Gold with amount
+  /// Coin with amount
   ///
   /// In en, this message translates to:
-  /// **'Gold: {amount}'**
+  /// **'Coin: {amount}'**
   String goldAmount(int amount);
 
   /// Prologue plot stage