revert: 移除 CONN_HEALTH_CHECKS（远程库每条请求多打一次 SQL）；加可选慢请求追踪

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

deploy/apply-lag-fix.sh

@@ -16,14 +16,6 @@ sleep 2
 systemctl is-active gunicorn-dianjing.service
 pgrep -cf 'gunicorn.*a_long_dianjing' || true
 
-echo ""
-echo ">>> 安装 worker 保活 cron（空闲后不卡）"
-chmod +x deploy/gunicorn-warmup.sh
-cp deploy/gunicorn-warmup.cron /etc/cron.d/gunicorn-warmup
-chmod 644 /etc/cron.d/gunicorn-warmup
-bash deploy/gunicorn-warmup.sh
-echo "  cron 已安装，每2分钟预热 worker"
-
 echo ""
 echo ">>> 最近慢请求 (rt>=0.5s):"
 grep -a 'hqhd' "$NGINX_LOG" | awk 'match($0,/rt=([0-9.]+)/,a){if(a[1]+0>=0.5)print}' | tail -5

deploy/disable-slow-trace.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+# 关闭慢请求追踪
+rm -f /etc/systemd/system/gunicorn-dianjing.service.d/slow-trace.conf
+systemctl daemon-reload
+systemctl restart gunicorn-dianjing.service
+echo "慢请求追踪已关闭"

deploy/enable-slow-trace.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+# 开启慢请求追踪（只写日志，不改业务逻辑）。卡的时候跑这个，操作小程序，再 cat 日志。
+set -e
+SVC=/etc/systemd/system/gunicorn-dianjing.service
+mkdir -p /etc/systemd/system/gunicorn-dianjing.service.d
+cat > /etc/systemd/system/gunicorn-dianjing.service.d/slow-trace.conf <<'EOF'
+[Service]
+Environment=SLOW_REQUEST_TRACE=1
+Environment=SLOW_REQUEST_THRESHOLD_MS=200
+Environment=SLOW_REQUEST_LOG=/tmp/slow-request-trace.log
+EOF
+: > /tmp/slow-request-trace.log
+systemctl daemon-reload
+systemctl restart gunicorn-dianjing.service
+echo "已开启。现在去小程序复现卡顿，然后执行:"
+echo "  cat /tmp/slow-request-trace.log"
+echo "关闭: bash deploy/disable-slow-trace.sh"