fix(observability): restore 24h capacity/network/disk trends via CH hourly agg

Node and dashboard 24h capacity, network, and disk IO charts only used the
latest limited raw snapshots (120/500 rows), so historical hour buckets stayed
empty. Prefer ClickHouse hourly aggregates with counter deltas, and fall back
to raw snapshots when aggregation is unavailable.

docs/changelog/index.md

@@ -18,6 +18,10 @@ sidebar: false
 
 ## [unreleased]
 
+### 修复
+
+- 修复节点/仪表盘 24 小时容量、网络、磁盘 IO 趋势在 ClickHouse 限流查询下几乎为空的问题：改为基于 `of_node_metric_snapshots` / `of_node_obs_openresty` 的小时级聚合构建趋势；主机与 OpenResty 累计计数器改为按小时 delta 统计。
+
 ## [v3.1.1] - 2026-07-06
 
 ### 修改