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/failure-drill.sh

@@ -0,0 +1,89 @@
+#!/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"
+
+drill=${1:-}
+confirmation=${2:-}
+[[ $confirmation == --execute ]] || {
+  echo 'usage: failure-drill.sh {api|database|witness} --execute' >&2
+  exit 64
+}
+load_cluster_env
+
+case $drill in
+  api)
+    started=$(date +%s)
+    pod=$(cluster_ssh "$CLUSTER_NINGBO_HOST" \
+      "k3s kubectl get pods -n easyai -l app.kubernetes.io/name=easyai-api,easyai.io/site=ningbo -o jsonpath='{.items[0].metadata.name}'")
+    cluster_ssh "$CLUSTER_NINGBO_HOST" \
+      "k3s kubectl delete pod '$pod' -n easyai --wait=false >/dev/null"
+    for _ in $(seq 1 20); do
+      if curl -fsS --max-time 3 --resolve "ai.51easyai.com:443:${CLUSTER_NINGBO_HOST#*@}" \
+        https://ai.51easyai.com/api/v1/readyz | grep -q '"ok":true'; then
+        elapsed=$(( $(date +%s) - started ))
+        break
+      fi
+      sleep 1
+    done
+    [[ ${elapsed:-99} -le 10 ]]
+    echo "api_failure_drill=PASS failover_seconds=$elapsed"
+    ;;
+  database)
+    old_primary=$(cluster_ssh "$CLUSTER_NINGBO_HOST" \
+      "k3s kubectl get cluster easyai-postgres -n easyai -o jsonpath='{.status.currentPrimary}'")
+    started=$(date +%s)
+    cluster_ssh "$CLUSTER_NINGBO_HOST" \
+      "k3s kubectl delete pod '$old_primary' -n easyai --grace-period=0 --force >/dev/null"
+    for _ in $(seq 1 150); do
+      new_primary=$(cluster_ssh "$CLUSTER_NINGBO_HOST" \
+        "k3s kubectl get cluster easyai-postgres -n easyai -o jsonpath='{.status.currentPrimary}'")
+      if [[ -n $new_primary && $new_primary != "$old_primary" ]]; then
+        elapsed=$(( $(date +%s) - started ))
+        break
+      fi
+      sleep 2
+    done
+    [[ ${elapsed:-999} -le 300 ]]
+    curl -fsS --max-time 10 https://ai.51easyai.com/api/v1/readyz | grep -q '"ok":true'
+    cluster_ssh "$CLUSTER_NINGBO_HOST" bash -s -- "$new_primary" <<'REMOTE'
+set -euo pipefail
+primary=$1
+k3s kubectl exec -n easyai "$primary" -c postgres -- \
+  psql -X -v ON_ERROR_STOP=1 -U easyai -d easyai_ai_gateway -c \
+  "INSERT INTO system_settings(setting_key,value) VALUES('ha_acceptance_probe',jsonb_build_object('at',now())) ON CONFLICT(setting_key) DO UPDATE SET value=excluded.value,updated_at=now();" >/dev/null
+for _ in $(seq 1 180); do
+  if [[ $(k3s kubectl get cluster easyai-postgres -n easyai -o jsonpath='{.status.readyInstances}') == 2 ]]; then
+    replication=$(k3s kubectl exec -n easyai "$primary" -c postgres -- \
+      psql -X -U easyai -d easyai_ai_gateway -At -c \
+      "SELECT count(*) FROM pg_stat_replication WHERE sync_state IN ('sync','quorum');")
+    [[ $replication == 1 ]] && break
+  fi
+  sleep 2
+done
+[[ ${replication:-0} == 1 ]]
+k3s kubectl exec -n easyai "$primary" -c postgres -- \
+  psql -X -v ON_ERROR_STOP=1 -U easyai -d easyai_ai_gateway -c \
+  "DELETE FROM system_settings WHERE setting_key='ha_acceptance_probe';" >/dev/null
+REMOTE
+    echo "database_failure_drill=PASS promotion_seconds=$elapsed old_primary=$old_primary new_primary=$new_primary"
+    ;;
+  witness)
+    cluster_ssh "$CLUSTER_LOS_ANGELES_HOST" 'systemctl stop k3s'
+    trap 'cluster_ssh "$CLUSTER_LOS_ANGELES_HOST" "systemctl start k3s" || true' EXIT HUP INT TERM
+    cluster_ssh "$CLUSTER_NINGBO_HOST" \
+      "k3s kubectl get --raw='/readyz?verbose' | grep -q '\\[+\\]etcd ok'"
+    curl -fsS --max-time 10 https://ai.51easyai.com/api/v1/readyz | grep -q '"ok":true'
+    cluster_ssh "$CLUSTER_LOS_ANGELES_HOST" 'systemctl start k3s'
+    cluster_ssh "$CLUSTER_NINGBO_HOST" \
+      'k3s kubectl wait --for=condition=Ready node/easyai-los-angeles --timeout=180s'
+    trap - EXIT HUP INT TERM
+    echo 'witness_failure_drill=PASS quorum_retained=true'
+    ;;
+  *)
+    echo 'drill must be api, database, or witness' >&2
+    exit 64
+    ;;
+esac