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/workers/daily_digest.py

@@ -0,0 +1,146 @@
+"""일일 다이제스트 워커 — PostgreSQL/CalDAV 쿼리 → Markdown + SMTP
+
+v1 scripts/pkm_daily_digest.py에서 포팅.
+DEVONthink/OmniFocus → PostgreSQL/CalDAV 쿼리로 전환.
+"""
+
+import os
+from datetime import datetime, timezone
+from pathlib import Path
+
+from sqlalchemy import func, select, text
+
+from core.config import settings
+from core.database import async_session
+from core.utils import send_smtp_email, setup_logger
+from models.document import Document
+from models.queue import ProcessingQueue
+
+logger = setup_logger("daily_digest")
+
+
+async def run():
+    """일일 다이제스트 생성 + 저장 + 발송"""
+    today = datetime.now(timezone.utc).strftime("%Y-%m-%d")
+    sections = []
+
+    async with async_session() as session:
+        # ─── 1. 오늘 추가된 문서 ───
+        added = await session.execute(
+            select(Document.ai_domain, func.count(Document.id))
+            .where(func.date(Document.created_at) == today)
+            .group_by(Document.ai_domain)
+        )
+        added_rows = added.all()
+        total_added = sum(row[1] for row in added_rows)
+
+        section = f"## 오늘 추가된 문서 ({total_added}건)\n"
+        if added_rows:
+            for domain, count in added_rows:
+                section += f"- {domain or '미분류'}: {count}건\n"
+        else:
+            section += "- 없음\n"
+        sections.append(section)
+
+        # ─── 2. 법령 변경 ───
+        law_docs = await session.execute(
+            select(Document.title)
+            .where(
+                Document.source_channel == "law_monitor",
+                func.date(Document.created_at) == today,
+            )
+        )
+        law_rows = law_docs.scalars().all()
+        section = f"## 법령 변경 ({len(law_rows)}건)\n"
+        if law_rows:
+            for title in law_rows:
+                section += f"- {title}\n"
+        else:
+            section += "- 변경 없음\n"
+        sections.append(section)
+
+        # ─── 3. 이메일 수집 ───
+        email_count = await session.execute(
+            select(func.count(Document.id))
+            .where(
+                Document.source_channel == "email",
+                func.date(Document.created_at) == today,
+            )
+        )
+        email_total = email_count.scalar() or 0
+        sections.append(f"## 이메일 수집\n- {email_total}건 아카이브\n")
+
+        # ─── 4. 처리 파이프라인 상태 ───
+        queue_stats = await session.execute(
+            text("""
+                SELECT stage, status, COUNT(*)
+                FROM processing_queue
+                WHERE created_at > NOW() - INTERVAL '24 hours'
+                GROUP BY stage, status
+                ORDER BY stage, status
+            """)
+        )
+        queue_rows = queue_stats.all()
+        section = "## 파이프라인 상태 (24h)\n"
+        if queue_rows:
+            for stage, status, count in queue_rows:
+                section += f"- {stage}/{status}: {count}건\n"
+        else:
+            section += "- 처리 항목 없음\n"
+
+        # 실패 건수 강조
+        failed = await session.execute(
+            select(func.count())
+            .select_from(ProcessingQueue)
+            .where(
+                ProcessingQueue.status == "failed",
+                ProcessingQueue.created_at > text("NOW() - INTERVAL '24 hours'"),
+            )
+        )
+        failed_count = failed.scalar() or 0
+        if failed_count > 0:
+            section += f"\n⚠️ **실패 {failed_count}건** — 수동 확인 필요\n"
+        sections.append(section)
+
+        # ─── 5. Inbox 미분류 ───
+        inbox_count = await session.execute(
+            select(func.count(Document.id))
+            .where(Document.file_path.like("PKM/Inbox/%"))
+        )
+        inbox_total = inbox_count.scalar() or 0
+        if inbox_total > 0:
+            sections.append(f"## Inbox 미분류\n- {inbox_total}건 대기 중\n")
+
+    # ─── Markdown 조합 ───
+    date_display = datetime.now(timezone.utc).strftime("%Y년 %m월 %d일")
+    markdown = f"# PKM 일일 다이제스트 — {date_display}\n\n"
+    markdown += "\n".join(sections)
+    markdown += f"\n---\n*생성: {datetime.now(timezone.utc).isoformat()}*\n"
+
+    # ─── NAS 저장 ───
+    digest_dir = Path(settings.nas_mount_path) / "PKM" / "Archive" / "digests"
+    digest_dir.mkdir(parents=True, exist_ok=True)
+    digest_path = digest_dir / f"{today}_digest.md"
+    digest_path.write_text(markdown, encoding="utf-8")
+
+    # ─── 90일 초과 아카이브 ───
+    archive_dir = digest_dir / "archive"
+    archive_dir.mkdir(exist_ok=True)
+    cutoff = datetime.now(timezone.utc).timestamp() - (90 * 86400)
+    for old in digest_dir.glob("*_digest.md"):
+        if old.stat().st_mtime < cutoff:
+            old.rename(archive_dir / old.name)
+
+    # ─── SMTP 발송 ───
+    smtp_host = os.getenv("MAILPLUS_HOST", "")
+    smtp_port = int(os.getenv("MAILPLUS_SMTP_PORT", "465"))
+    smtp_user = os.getenv("MAILPLUS_USER", "")
+    smtp_pass = os.getenv("MAILPLUS_PASS", "")
+    if smtp_host and smtp_user:
+        send_smtp_email(
+            smtp_host, smtp_port, smtp_user, smtp_pass,
+            f"PKM 다이제스트 — {date_display}",
+            markdown,
+        )
+
+    logger.info(f"다이제스트 생성 완료: {digest_path}")