infra: 自动定时任务 — cron 服务

新增:
  - scripts/cron_entrypoint.py: 纯 Python 调度器, 零依赖
    任务1: 每天 03:00 跑 archive_old_tasks.py --apply
    任务2: 每周一 03:10 VACUUM ANALYZE (维护表统计信息)
  - docker-compose.yml: 加 cron 服务 (共享 meshsafe:latest 镜像)

归档策略 (archive_old_tasks.py):
  - scan_tasks  90天前: 清 detail JSONB (省空间)
  - scan_tasks  365天前: 移到 scan_tasks_archive
  - idempotency_records:  清 7 天前 (幂等 TTL)
  - policy_versions:      只留最新 5 个

启动: docker compose up -d cron
日志: docker compose logs -f cron
docker compose up 会自动拉起 (restart: unless-stopped)

scripts/cron_entrypoint.py

@@ -0,0 +1,121 @@
+"""MeshSafe 定时任务调度器 — 零依赖，Docker 容器前台常驻。
+
+和 api 共享同一个镜像，容器 entrypoint 换成本脚本即可。
+用法: docker run meshsafe:latest python3 scripts/cron_entrypoint.py
+
+支持的任务:
+  每天 03:00 归档 + 清理 DB (archive_old_tasks.py --apply)
+  每周一 03:10 VACUUM ANALYZE (维护表统计信息)
+"""
+from __future__ import annotations
+
+import logging
+import os
+import subprocess
+import sys
+import time
+from datetime import datetime, timedelta
+
+sys.path.insert(0, "/app")
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s [%(levelname)s] %(message)s",
+)
+log = logging.getLogger("scheduler")
+
+
+def run(cmd: list[str], label: str) -> None:
+    """跑一个命令，捕获输出并记日志。"""
+    log.info(f"[{label}] 开始执行: {' '.join(cmd)}")
+    try:
+        proc = subprocess.run(cmd, capture_output=True, text=True, timeout=1800)
+        if proc.stdout:
+            for line in proc.stdout.strip().splitlines():
+                log.info(f"[{label}] {line}")
+        if proc.stderr:
+            for line in proc.stderr.strip().splitlines():
+                log.warning(f"[{label}] {line}")
+        if proc.returncode == 0:
+            log.info(f"[{label}] ✅ 完成")
+        else:
+            log.error(f"[{label}] ❌ 返回码 {proc.returncode}")
+    except subprocess.TimeoutExpired:
+        log.error(f"[{label}] ❌ 超时 (30min)")
+    except Exception as e:
+        log.error(f"[{label}] ❌ 异常: {e}")
+
+
+def run_vacuum() -> None:
+    """VACUUM ANALYZE — 维护表统计信息。"""
+    try:
+        from app.db import engine
+        from sqlalchemy import text
+
+        tables = [
+            "scan_tasks", "scan_tasks_archive",
+            "scan_findings", "idempotency_records",
+            "policy_versions", "audit_logs",
+        ]
+        with engine.begin() as conn:
+            for tbl in tables:
+                log.info(f"[VACUUM] {tbl} ...")
+                conn.execute(text(f"VACUUM ANALYZE {tbl}"))
+        log.info("[VACUUM] ✅ 全部完成")
+    except Exception as e:
+        log.error(f"[VACUUM] ❌ 异常: {e}")
+
+
+def seconds_until(target_hour: int, target_minute: int, weekday: int | None = None) -> float:
+    """计算到下次目标时间的秒数。
+
+    weekday: 0=周一...6=周日, None=每天
+    """
+    now = datetime.now()
+    candidate = now.replace(hour=target_hour, minute=target_minute, second=0, microsecond=0)
+
+    if weekday is not None:
+        # 找到本周目标日
+        days_ahead = weekday - now.weekday()
+        if days_ahead < 0 or (days_ahead == 0 and now >= candidate):
+            days_ahead += 7
+        candidate += timedelta(days=days_ahead)
+    else:
+        if candidate <= now:
+            candidate += timedelta(days=1)
+
+    return (candidate - now).total_seconds()
+
+
+def main() -> None:
+    log.info("=" * 60)
+    log.info("MeshSafe 定时任务调度器启动")
+    log.info(f"PID={os.getpid()}  TZ=Asia/Shanghai")
+    log.info("任务:")
+    log.info("  - 每天 03:00  archive_old_tasks.py --apply")
+    log.info("  - 每周一 03:10 VACUUM ANALYZE")
+    log.info("=" * 60)
+
+    while True:
+        # 计算两个任务下次执行时间，取更早的那个
+        secs_archive = seconds_until(3, 0, weekday=None)      # 每天 03:00
+        secs_vacuum = seconds_until(3, 10, weekday=0)          # 周一 03:10
+
+        if secs_archive <= secs_vacuum:
+            log.info(f"下一个任务: 归档 → {secs_archive/3600:.1f}h 后")
+            time.sleep(secs_archive)
+            run(
+                [sys.executable, "/app/scripts/archive_old_tasks.py", "--apply"],
+                "ARCHIVE",
+            )
+            # 跑完后清下一次时间 (避免在 03:00 这一刻两个任务重叠)
+            continue
+        else:
+            log.info(f"下一个任务: VACUUM → {secs_vacuum/3600:.1f}h 后")
+            time.sleep(secs_vacuum)
+            run_vacuum()
+            continue
+
+
+if __name__ == "__main__":
+    main()