feat(tkuser): 협력업체 완전삭제 기능 추가 (admin 전용)

- 관련 데이터 cascade 삭제 (workers, schedules, checkins, reports, SSO 계정 등)
- 구매 이력 있는 업체는 삭제 차단
- 프론트엔드: 목록/상세에 완전삭제 버튼 + prompt("삭제") 안전장치

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

user-management/api/routes/partnerRoutes.js

@@ -6,6 +6,8 @@ const ctrl = require('../controllers/partnerController');
 router.use(requireAuth);
 
 router.get('/', ctrl.list);
+router.get('/:id/delete-info', requireAdmin, ctrl.getDeleteInfo);
+router.delete('/:id/permanent', requireAdmin, ctrl.permanentDelete);
 router.get('/:id', ctrl.getById);
 router.post('/', requireAdmin, ctrl.create);
 router.put('/:id', requireAdmin, ctrl.update);