feat: not available purchase itmes/#706

[hjbin-25]

변경사항

• 구매 불가능한 아이템 기능 추가
• 현재 존재하는 아이템을 isAblePurchase = true로 설정
• 관련 테스트 로직 수정

관련 이슈

Closes #706

추가 컨텍스트

현재 남아있는 데이터와 충돌 여부만 확인해주세요

[gemini-code-assist]

Code Review

This pull request introduces a new field, isAblePurchase, to the product entity across all layers, including the database schema, JPA entities, domain models, and DTOs. This field allows administrators to control whether a product is currently available for purchase, and the CreatePurchaseService has been updated to enforce this restriction by throwing a new NotAblePurchaseException when applicable. The review feedback suggests renaming the field to isPurchasable for better grammatical clarity and switching from the Boolean wrapper class to the primitive boolean type to improve type safety and prevent potential NullPointerException issues during unboxing.