feat: implement Phase 3 automation workers

- Add automation_state table for incremental sync (last UID, last check)
- Add law_monitor worker: 국가법령정보센터 API → NAS/DB/CalDAV VTODO
  (LAW_OC 승인 대기 중, 코드 완성)
- Add mailplus_archive worker: IMAP(993) → .eml NAS save + DB + SMTP
  notification (imaplib via asyncio.to_thread, timeout=30)
- Add daily_digest worker: PostgreSQL/pipeline stats → Markdown + SMTP
  (documents, law changes, email, queue errors, inbox backlog)
- Add CalDAV VTODO helper and SMTP email helper to core/utils.py
- Wire 3 cron jobs in APScheduler (law@07:00, mail@07:00+18:00,
  digest@20:00) with timezone=Asia/Seoul

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

app/main.py

@@ -19,16 +19,26 @@ from models.user import User
 async def lifespan(app: FastAPI):
     """앱 시작/종료 시 실행되는 lifespan 핸들러"""
     from apscheduler.schedulers.asyncio import AsyncIOScheduler
+    from apscheduler.triggers.cron import CronTrigger
+    from workers.daily_digest import run as daily_digest_run
     from workers.file_watcher import watch_inbox
+    from workers.law_monitor import run as law_monitor_run
+    from workers.mailplus_archive import run as mailplus_run
     from workers.queue_consumer import consume_queue
 
     # 시작: DB 연결 확인
     await init_db()
 
     # APScheduler: 백그라운드 작업
-    scheduler = AsyncIOScheduler()
+    scheduler = AsyncIOScheduler(timezone="Asia/Seoul")
+    # 상시 실행
     scheduler.add_job(consume_queue, "interval", minutes=1, id="queue_consumer")
     scheduler.add_job(watch_inbox, "interval", minutes=5, id="file_watcher")
+    # 일일 스케줄 (KST)
+    scheduler.add_job(law_monitor_run, CronTrigger(hour=7), id="law_monitor")
+    scheduler.add_job(mailplus_run, CronTrigger(hour=7), id="mailplus_morning")
+    scheduler.add_job(mailplus_run, CronTrigger(hour=18), id="mailplus_evening")
+    scheduler.add_job(daily_digest_run, CronTrigger(hour=20), id="daily_digest")
     scheduler.start()
 
     yield