feat(tkuser): Sprint 001 Section A — 연차/휴가 백엔드 전환 (DB + API)

workers/vacation_balance_details → sso_users/sp_vacation_balances 기반 전환.
부서장 설정, 승인권한 CRUD, vacation_settings 테이블, 장기근속 자동부여,
startup migration 추가.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

user-management/api/routes/departmentRoutes.js

@@ -13,4 +13,9 @@ router.post('/', requireAdmin, departmentController.create);
 router.put('/:id', requireAdmin, departmentController.update);
 router.delete('/:id', requireAdmin, departmentController.remove);
 
+// 승인권한 (Approval Authority)
+router.get('/:id/approval-authorities', requireAuth, departmentController.getApprovalAuthorities);
+router.post('/:id/approval-authorities', requireAdmin, departmentController.createApprovalAuthority);
+router.delete('/:id/approval-authorities/:authId', requireAdmin, departmentController.deleteApprovalAuthority);
+
 module.exports = router;