feat: live последние события на Dashboard; retention, health, runbook

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/systemd/sac-retention.service

@@ -0,0 +1,16 @@
+[Unit]
+Description=Security Alert Center data retention
+After=network-online.target postgresql.service
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+User=sac
+Group=sac
+WorkingDirectory=/opt/security-alert-center/backend
+EnvironmentFile=/opt/security-alert-center/config/sac-api.env
+ExecStart=/opt/security-alert-center/backend/.venv/bin/python -m app.jobs.retention
+Nice=10
+
+[Install]
+WantedBy=multi-user.target

deploy/systemd/sac-retention.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=Daily SAC retention purge
+
+[Timer]
+OnCalendar=daily
+RandomizedDelaySec=900
+Persistent=true
+
+[Install]
+WantedBy=timers.target