ALTER TABLE lead_contract_data
    ADD COLUMN negotiated_at DATETIME NULL AFTER evaluated_by,
    ADD COLUMN negotiated_by INT UNSIGNED NULL AFTER negotiated_at,
    ADD COLUMN negotiated_reason VARCHAR(60) NULL AFTER negotiated_by,
    ADD CONSTRAINT fk_contract_data_negotiated_user FOREIGN KEY (negotiated_by) REFERENCES users (id) ON DELETE SET NULL,
    ADD INDEX idx_contract_data_negotiated_at (negotiated_at);
