perf,feat(events),ops: third optimization pass

Overview cold start:
- InstanceResourceService persists every live fetch into status_snapshots
  (category 'resources') and serves a snapshot younger than 2 minutes
  before calling upstream, so the first fleet overview after a restart
  costs zero device requests; instance deletion cleans up via FK cascade

Bounded retention for the four fastest-growing tables (15-minute sweep):
- connection_logs: one row per probe per beat had no automatic cleanup
- audit_events: new pruneBefore (90d)
- operation_preparations: every prepare/retry attempt inserted a row,
  terminal rows now expire after 7 days
- notification_queue: terminal rows pruned after 30 days

SSE events now cover instance lifecycle:
- create/update emit instance envelopes from the routes; the two-phase
  delete emits a job envelope on every terminal transition plus an
  instance envelope when the node actually disappears, so fleet and
  instance views invalidate in real time

Linux ops:
- 'install.sh unit' writes systemd user units for API and gateway with
  Restart=on-failure, 0600 secret injection, and
  MULTI_SIMADMIN_SYSTEMD_UNIT wired so console self-update restarts via
  systemctl -- closing the self-update loop on Linux

scripts/install.sh

@@ -36,6 +36,7 @@ Multi SimAdmin 一键安装与服务管理
   restart    停止后重新启动
   status     显示进程、端口与健康状态
   uninstall  卸载程序，默认保留数据、令牌和日志
+  unit       （仅 Linux）生成 systemd 用户单元，支持开机自启与在线自更新重启
 环境变量：
   MULTI_SIMADMIN_HOME           安装根目录（默认 macOS 为 ~/Library/Application Support/multi-simadmin，Linux 为 ~/.local/share/multi-simadmin）
   MULTI_SIMADMIN_ALLOWED_HOSTS  额外允许的 LAN 主机名/IP，逗号分隔
@@ -297,6 +298,72 @@ uninstall_app() {
   say "程序已卸载；默认保留数据、Gateway token 和日志：$APP_ROOT"
 }
 
+write_systemd_units() {
+  require_platform
+  [ "$PLATFORM" = Linux ] || die "systemd 单元仅适用于 Linux"
+  command -v systemctl >/dev/null 2>&1 || die "缺少 systemctl"
+  [ -f "$SOURCE_DIR/apps/web/dist/index.html" ] || die "尚未安装，请先运行 install"
+  [ -f "$TOKEN_FILE" ] || die "缺少 Gateway token，请先运行 install"
+  node_bin=$(command -v node)
+  unit_dir=${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user
+  mkdir -p "$unit_dir"
+  chmod 700 "$unit_dir"
+
+  env_file="$APP_ROOT/service-env"
+  { printf 'MULTI_SIMADMIN_GATEWAY_TOKEN='; cat "$TOKEN_FILE"; } >"$env_file"
+  chmod 600 "$env_file"
+
+  cat >"$unit_dir/multi-simadmin-api.service" <<EOF
+[Unit]
+Description=Multi SimAdmin control-plane API
+After=network.target
+
+[Service]
+WorkingDirectory=$SOURCE_DIR
+ExecStart=$node_bin --import tsx $SOURCE_DIR/apps/api/src/production-cli.ts
+Restart=on-failure
+RestartSec=3
+Environment=MULTI_SIMADMIN_DATA_ROOT=$DATA_ROOT
+Environment=MULTI_SIMADMIN_DATABASE_PATH=$DATA_ROOT/control-plane.sqlite3
+Environment=MULTI_SIMADMIN_SECRET_BACKEND=secret-file
+Environment=MULTI_SIMADMIN_SYSTEMD_UNIT=multi-simadmin-api.service
+EnvironmentFile=$env_file
+UMask=0077
+
+[Install]
+WantedBy=default.target
+EOF
+
+  cat >"$unit_dir/multi-simadmin-gateway.service" <<EOF
+[Unit]
+Description=Multi SimAdmin LAN gateway
+After=network.target multi-simadmin-api.service
+
+[Service]
+WorkingDirectory=$SOURCE_DIR
+ExecStart=$node_bin --import tsx $SOURCE_DIR/apps/api/src/production-gateway-cli.ts
+Restart=on-failure
+RestartSec=3
+Environment=MULTI_SIMADMIN_CUTOVER_ACK=I ACKNOWLEDGE MULTI-SIMADMIN OWNS PORT 8788
+Environment=MULTI_SIMADMIN_GATEWAY_HOST=0.0.0.0
+Environment=MULTI_SIMADMIN_GATEWAY_ALLOWED_HOSTS=$(allowed_hosts)
+Environment=CANARY_DIST_DIR=$SOURCE_DIR/apps/web/dist
+Environment=CANARY_UPSTREAM_PORT=8790
+Environment=MULTI_SIMADMIN_SYSTEMD_UNIT=multi-simadmin-gateway.service
+EnvironmentFile=$env_file
+UMask=0077
+
+[Install]
+WantedBy=default.target
+EOF
+
+  chmod 600 "$unit_dir/multi-simadmin-api.service" "$unit_dir/multi-simadmin-gateway.service"
+  systemctl --user daemon-reload
+  say "已写入 systemd 用户单元。启用自启动并启动："
+  say "  systemctl --user enable --now multi-simadmin-api.service multi-simadmin-gateway.service"
+  say "注意：由 systemd 托管后请用 systemctl 管理，不要再用本脚本 start/stop，避免双进程争抢端口。"
+}
+
 command=${1:-install}
 case "$command" in
   install) install_app ;;
@@ -305,6 +372,7 @@ case "$command" in
   restart) stop_service; start_service ;;
   status) status_service ;;
   uninstall) uninstall_app ;;
+  unit) write_systemd_units ;;
   help|-h|--help) usage ;;
   *) usage >&2; exit 2 ;;
 esac