fix: 업무현황 저장 시 report_date 누락 버그 수정

submitWorkReport에서 API 필수값인 report_date를 전송하지 않아
"보고일은 필수입니다" 에러 발생. 오늘 날짜를 자동으로 설정.

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

tkpurchase/web/static/js/tkpurchase-partner-portal.js

@@ -196,6 +196,7 @@ async function submitWorkReport(checkinId, scheduleId) {
     const body = {
         checkin_id: checkinId,
         schedule_id: scheduleId,
+        report_date: new Date().toISOString().substring(0, 10),
         actual_workers: parseInt(document.getElementById('reportWorkers_' + checkinId).value) || 0,
         work_content: workContent,
         progress_rate: parseInt(document.getElementById('reportProgress_' + checkinId).value) || 0,