feat(deploy): 切换宁波单节点生产拓扑

移除已停用的香港 API、Web、Worker 和边缘 Service 渲染结果，将 Worker 与容量控制器固定到宁波单实例，并在发布成功后清理旧香港资源。\n\n容量控制器忽略最大副本为零的站点，集群环境允许不再声明香港主机；单节点 production acceptance 不再依赖香港 Service、Deployment 或 SSH 回退。\n\n验证：Go 全量测试与 go vet；迁移安全检查；Kustomize 单节点渲染；ShellCheck；cluster release、production acceptance 和 manual release 测试。

scripts/cluster/common.sh

@@ -24,16 +24,14 @@ load_cluster_env() {
   cluster_ssh_key=${AI_GATEWAY_CLUSTER_SSH_KEY:-$cluster_ssh_key}
 
   : "${AI_GATEWAY_DEPLOY_HOST:?}"
-  : "${AI_GATEWAY_DEPLOY_HOST_2:?}"
-  : "${AI_GATEWAY_DEPLOY_HOST_3:?}"
   : "${ALI_KEY:?}"
   : "${ALI_SECRET:?}"
   : "${ALI_REGION:?}"
   : "${ALI_BUCKET:?}"
 
   CLUSTER_NINGBO_HOST=${AI_GATEWAY_NINGBO_HOST:-$AI_GATEWAY_DEPLOY_HOST}
-  CLUSTER_LOS_ANGELES_HOST=${AI_GATEWAY_LOS_ANGELES_HOST:-$AI_GATEWAY_DEPLOY_HOST_2}
-  CLUSTER_HONGKONG_HOST=${AI_GATEWAY_HONGKONG_HOST:-$AI_GATEWAY_DEPLOY_HOST_3}
+  CLUSTER_LOS_ANGELES_HOST=${AI_GATEWAY_LOS_ANGELES_HOST:-${AI_GATEWAY_DEPLOY_HOST_2:-}}
+  CLUSTER_HONGKONG_HOST=${AI_GATEWAY_HONGKONG_HOST:-${AI_GATEWAY_DEPLOY_HOST_3:-}}
   CLUSTER_WORKER_NODE_4_HOST=${AI_GATEWAY_WORKER_NODE_4_HOST:-}
   CLUSTER_WORKER_NODE_4_NAME=${AI_GATEWAY_WORKER_NODE_4_NAME:-}
   CLUSTER_WORKER_NODE_4_SITE=${AI_GATEWAY_WORKER_NODE_4_SITE:-}
@@ -46,6 +44,7 @@ load_cluster_env() {
   export CLUSTER_WORKER_NODE_4_ENABLED
 
   for host in "$CLUSTER_NINGBO_HOST" "$CLUSTER_HONGKONG_HOST" "$CLUSTER_LOS_ANGELES_HOST"; do
+    [[ -n $host ]] || continue
     [[ $host =~ ^root@[A-Za-z0-9.-]+$ ]] || {
       echo "cluster hosts must use root@host syntax" >&2
       return 1