feat: 외교부 기능 추가 및 외교 문서 관련 데이터베이스 모델 생성

packages/infra/src/db.ts

@@ -9,6 +9,7 @@ export interface DatabaseClient {
     city: GamePrisma.CityDelegate;
     nation: GamePrisma.NationDelegate;
     diplomacy: GamePrisma.DiplomacyDelegate;
+    diplomacyLetter: GamePrisma.DiplomacyLetterDelegate;
     generalTurn: GamePrisma.GeneralTurnDelegate;
     nationTurn: GamePrisma.NationTurnDelegate;
     troop: GamePrisma.TroopDelegate;