feat(tkpurchase): 체크인 worker_names 배열 저장 + 구매팀 체크인 관리 기능

- doCheckIn()에서 worker_names를 콤마 split 배열로 전송 (DB에 JSON 배열로 저장)
- 구매팀 일정 페이지에 체크인 조회/수정/삭제 모달 추가
- DELETE /checkins/:id endpoint + 트랜잭션 삭제 (reports cascade)
- PUT /checkins/:id에 requirePage 권한 guard 추가

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

tkpurchase/api/routes/checkinRoutes.js

@@ -1,6 +1,6 @@
 const express = require('express');
 const router = express.Router();
-const { requireAuth } = require('../middleware/auth');
+const { requireAuth, requirePage } = require('../middleware/auth');
 const ctrl = require('../controllers/checkinController');
 
 router.use(requireAuth);
@@ -10,6 +10,7 @@ router.get('/schedule/:scheduleId', ctrl.list);
 router.get('/my', ctrl.myCheckins); // partner portal
 router.post('/', ctrl.checkIn); // partner can do this
 router.put('/:id/checkout', ctrl.checkOut);
-router.put('/:id', ctrl.update);
+router.put('/:id', requirePage('purchasing_schedule'), ctrl.update);
+router.delete('/:id', requirePage('purchasing_schedule'), ctrl.deleteCheckin);
 
 module.exports = router;