fix(cluster): 收敛宁波单实例数据库拓扑

将生产 CNPG 固定为宁波单实例，并显式关闭旧同步复制配置。发布流程在拓扑收敛前校验主库位置并创建 OSS 备份，应用后验证单实例、无复制连接和主库可用。同步更新生产监控、集群验收和发布脚本回归测试。

scripts/cluster/monitor-production-release.sh

@@ -246,11 +246,11 @@ while (( $(date +%s) - started_epoch < AI_GATEWAY_RELEASE_MONITOR_TOTAL_SECONDS
       if (value>max) max=value
     } END {printf "%.0f",max}')
   (( pod_max_memory < 1536 )) || failure_gate_id=${failure_gate_id:-pod_memory_hard}
-  [[ $(remote_kubectl get cluster easyai-postgres -n "$namespace" \
-    -o 'jsonpath={.status.readyInstances}') == 2 ]] || failure_gate_id=${failure_gate_id:-postgres_ready}
-  sync_state=$(database_query "SELECT COALESCE(string_agg(sync_state,','),'') FROM pg_stat_replication;")
-  [[ ",$sync_state," == *,sync,* || ",$sync_state," == *,quorum,* ]] ||
-    failure_gate_id=${failure_gate_id:-postgres_replication}
+  postgres_state=$(remote_kubectl get cluster easyai-postgres -n "$namespace" -o json |
+    jq -r '[.spec.instances, (.status.readyInstances // 0)] | @tsv')
+  [[ $postgres_state == $'1\t1' ]] || failure_gate_id=${failure_gate_id:-postgres_ready}
+  replica_count=$(database_query "SELECT count(*) FROM pg_stat_replication;")
+  [[ $replica_count == 0 ]] || failure_gate_id=${failure_gate_id:-postgres_replication}
   connections=$(database_query "SELECT count(*) FROM pg_stat_activity WHERE backend_type='client backend';")
   max_connections=$(database_query "SELECT setting::int FROM pg_settings WHERE name='max_connections';")
   (( connections < 150 && connections * 4 < max_connections * 3 )) ||