feat(sprint005): 월간 확인 워크플로우 — 관리자 확인요청 + 수정요청

- DB: status ENUM 확장 (review_sent, change_request) + reviewed_by/at, change_details
- API: POST /review-send (일괄 확인요청), POST /review-respond (수정 승인/거부)
- 작업자: pending=검토대기, review_sent=확인/수정요청, rejected=동의(재확인)
- 관리자: 필터 탭 확장 + 확인요청 일괄 발송 버튼
- confirm 상태 전환 검증: pending→confirmed 차단

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

system1-factory/api/index.js

@@ -48,7 +48,7 @@ async function runStartupMigrations() {
     const fs = require('fs');
     const path = require('path');
     const db = await getDb();
-    const migrationFiles = ['20260326_schedule_extensions.sql', '20260330_add_proxy_input_fields.sql', '20260330_create_monthly_work_confirmations.sql', '20260331_fix_deduct_days_precision.sql'];
+    const migrationFiles = ['20260326_schedule_extensions.sql', '20260330_add_proxy_input_fields.sql', '20260330_create_monthly_work_confirmations.sql', '20260331_fix_deduct_days_precision.sql', '20260401_monthly_confirm_workflow.sql'];
     for (const file of migrationFiles) {
       const sqlPath = path.join(__dirname, 'db', 'migrations', file);
       if (!fs.existsSync(sqlPath)) continue;