feat(deploy): 增加三节点 K3s 高可用迁移能力

新增 WireGuard 全互联、三 server embedded-etcd K3s、CloudNativePG 双实例、Barman OSS 备份、双 NGINX、Kubernetes Secret/RBAC 与本地旧文件按严格 24 小时清理。

新增维护窗口数据迁移、digest 固定滚动发布、应用回滚、跨节点文件 E2E、节点和数据库故障演练、CNPG 恢复与 etcd 快照验收脚本；洛杉矶仅作为带 NoSchedule 污点的仲裁节点。

所有生产 Secret 只在执行时从 0600 本地环境和旧生产容器导入，仓库不保存凭据；公网入口保持人工 DNS 故障切换边界。

验证：bash -n、ShellCheck、kubectl kustomize、Node 语法检查、Secret 扫描、OSS put/head/delete 实测。

scripts/cluster/install-certificate-sync.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+script_dir=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=scripts/cluster/common.sh
+source "$script_dir/common.sh"
+load_cluster_env
+
+public_key=$(cluster_ssh "$CLUSTER_NINGBO_HOST" 'bash -s' <<'REMOTE'
+set -euo pipefail
+install -d -m 0700 /root/.ssh
+if [[ ! -f /root/.ssh/id_ed25519_easyai_cert_sync ]]; then
+  ssh-keygen -q -t ed25519 -N '' -f /root/.ssh/id_ed25519_easyai_cert_sync
+fi
+cat /root/.ssh/id_ed25519_easyai_cert_sync.pub
+REMOTE
+)
+[[ $public_key == ssh-ed25519\ * ]] || {
+  echo 'invalid certificate sync public key' >&2
+  exit 1
+}
+cluster_ssh "$CLUSTER_HONGKONG_HOST" bash -s -- "$public_key" <<'REMOTE'
+set -euo pipefail
+public_key=$1
+install -d -m 0700 /root/.ssh
+touch /root/.ssh/authorized_keys
+chmod 0600 /root/.ssh/authorized_keys
+grep -Fqx "$public_key" /root/.ssh/authorized_keys || printf '%s\n' "$public_key" >>/root/.ssh/authorized_keys
+REMOTE
+
+cluster_scp "$script_dir/sync-nginx-certificate.sh" \
+  "$CLUSTER_NINGBO_HOST:/usr/local/sbin/easyai-sync-nginx-certificate"
+cluster_ssh "$CLUSTER_NINGBO_HOST" 'bash -s' <<'REMOTE'
+set -euo pipefail
+chmod 0750 /usr/local/sbin/easyai-sync-nginx-certificate
+install -d -m 0755 /etc/letsencrypt/renewal-hooks/deploy
+ln -sfn /usr/local/sbin/easyai-sync-nginx-certificate \
+  /etc/letsencrypt/renewal-hooks/deploy/easyai-sync-nginx-certificate
+/usr/local/sbin/easyai-sync-nginx-certificate
+REMOTE
+echo 'certificate_sync_install=PASS'