✨ 기능 추가: ERD 모델 삭제 기능 및 고도화

[seonghobae]

ERD 엔진(ERDModel)에서 이전에 지원하지 않던 테이블 삭제, 컬럼 삭제 기능을 추가하고 컬럼 속성(UNIQUE, DEFAULT) 정의를 구현했습니다.

• removeTable(name): 참조 무결성(다른 테이블의 외래키 참조 여부) 확인 후 테이블 삭제 기능 구현
• removeColumn(tableName, columnName): 참조 무결성 확인 및 해당 컬럼과 연결된 외래키를 자동 정리하는 기능 구현
• generateDDL: UNIQUE 제약조건과 DEFAULT 값 설정 문구 추가
• 테스트 코드(Vitest) 강화 및 100% 커버리지 달성 확인

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PR created automatically by Jules for task 15934554285530772683 started by @seonghobae

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