✅ template_id 컬럼이 이미 존재합니다!

현재 employment_contracts 테이블 구조:
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id | int | NOT NULL
contract_number | varchar(50) | NOT NULL
template_id | int | NULL
employee_id | int | NOT NULL
employee_name | varchar(100) | NOT NULL
employee_phone | varchar(20) | NULL
employee_email | varchar(100) | NULL
employee_address | text | NULL
contract_type | enum('regular','fixed_term','part_time') | NOT NULL
start_date | date | NOT NULL
end_date | date | NULL
probation_period | int | NULL
work_location | varchar(200) | NOT NULL
job_description | text | NOT NULL
work_hours | varchar(100) | NOT NULL
work_days | varchar(200) | NULL
base_salary | int | NOT NULL
salary_components | text | NULL
payment_method | varchar(100) | NOT NULL
payment_day | int | NOT NULL
break_time | varchar(100) | NOT NULL
holidays | text | NOT NULL
annual_leave | varchar(100) | NOT NULL
notes | text | NULL
contract_html | longtext | NULL
employee_signature | longtext | NULL
employee_signed_at | datetime | NULL
employee_ip | varchar(45) | NULL
employer_id | int | NOT NULL
employer_name | varchar(100) | NOT NULL
employer_signature | longtext | NULL
employer_signed_at | datetime | NULL
employer_ip | varchar(45) | NULL
status | enum('draft','employee_signed','completed','terminated') | NULL
content_hash | varchar(64) | NULL
delivered_at | datetime | NULL
delivery_method | varchar(50) | NULL
employee_consent_at | datetime | NULL
termination_date | date | NULL
retention_until | date | NULL
previous_contract_id | int | NULL
is_renewal | tinyint(1) | NULL
renewal_reason | varchar(200) | NULL
created_at | datetime | NULL
created_by | int | NOT NULL
updated_at | datetime | NULL