feat(topup-log): add NODE_NAME env var for audit logs

Introduce NODE_NAME environment variable to identify node identity in top-up
audit logs, improving readability over auto-detected container internal IPs
in Docker/K8s deployments. Surface node_name in admin expanded log rows and
add it as a commented example to docker-compose.yml.

model/log.go

@@ -118,6 +118,7 @@ func RecordTopupLog(userId int, content string, callerIp string, paymentMethod s
 	username, _ := GetUsernameById(userId, false)
 	adminInfo := map[string]interface{}{
 		"server_ip":               common.GetIp(),
+		"node_name":               common.NodeName,
 		"caller_ip":               callerIp,
 		"payment_method":          paymentMethod,
 		"callback_payment_method": callbackPaymentMethod,