feat(obs): 去掉宿主机网卡趋势，磁盘读写改按速率展示

Agent 不再采集网卡累计字节，看板与节点网络图仅保留访问日志已提供/接收。
磁盘 IO 按小时换算为 B/s 曲线，摘要为近 24 小时平均速率，并同步 Swagger。

internal/apps/relay/observability/collector.go

@@ -48,9 +48,8 @@ func BuildSnapshot(cfg *config.Config, stateStore *state.Store) *service.AgentNo
 
 	metric.MemoryTotalBytes, metric.MemoryUsedBytes = edgeobs.ReadMemInfo()
 	metric.StorageTotalBytes, metric.StorageUsedBytes = edgeobs.StatFilesystem(cfg.DataDir)
-	metric.NetworkRxBytes, metric.NetworkTxBytes = edgeobs.ReadLinuxNetworkTotals()
+	// Host NIC totals are not collected.
 	metric.DiskReadBytes, metric.DiskWriteBytes = edgeobs.ReadLinuxDiskTotals()
-
 	if stateStore == nil {
 		return metric
 	}