Add authentication schemas for user registration and login: - UserRegister: email, password (with strength validation), password_confirm - UserLogin: email, password - UserResponse: id, email, created_at, is_active (orm_mode=True) - TokenResponse: access_token, token_type, expires_in - TokenData: user_id, exp Includes field validators for password strength and password confirmation matching. Test coverage: 19 tests for all schemas