엔티티 생성 및 관계 설정

[x] UserAccounts 엔티티 생성
- user_id (PK), login_id, password, name
[x] BusinessProfiles 엔티티 생성
- profile_id (PK), user_id (FK), company, department, position, email, phone
[x] BusinessContacts 엔티티 생성
- contact_id (PK), user_id (FK), contact_user_id (FK)
[x] Posts 엔티티 생성
- post_id (PK), user_id (FK), image_url, content, created_at, post_like_count, comments_count
[x] Comments 엔티티 생성
- comment_id (PK), post_id (FK), user_id (FK), content, created_at, comment_like_count
[x] PostLikes 엔티티 생성
- post_like_id (PK), post_id (FK), user_id (FK), created_at
[x] CommentLikes 엔티티 생성
- comment_like_id (PK), comment_id (FK), user_id (FK), created_at

Introducing-developer-friends / Devlntro_api