- Added explicit getter/setter methods in User entity for use with service layer
- Implemented standard getters/setters in SignupRequest DTO
- Replaced incorrect imports from models.User to entity.User across services and repository
- Enforced alphanumeric-only usernames using regex validation.
- Passwords must be >= 8 chars and checked against haveibeenpwned.com.
- Improved SignupRequest DTO with validation annotations.
- Implemented UserService to handle password validation and encoding.