Creator entity with User relation

[Mimah97]

Add Creator entity with User relation

Summary

Introduces a Creator entity as a one-to-one extension of User when user.is_creator is true, for creator-specific fields without duplicating user data.

Changes

• User entity: Added id, email, is_creator, created_at, updated_at plus OneToOne relation to Creator
• Creator entity: id, user_id (unique FK to User), bio, subscription_price, currency, is_verified, created_at, updated_at
• Relation: OneToOne between User and Creator with onDelete: 'CASCADE' when User is deleted
• UsersModule: Registers User and Creator with TypeORM
• Docs: Entity comments and src/creators/README.md describing the relation and cascade behavior
• Test: Unit test to create Creator and load it with User

Acceptance criteria

• Creator entity exists and can be created/queried
• Relation to User works; creator loads with user
• Migration/sync runs without errors
• Cascade delete when User is deleted
• Index on user_id (unique constraint)
• is_creator on User documented as matching presence of Creator row
  closes Add Creators module – entity #30