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。

docs/swagger.yaml

@@ -714,10 +714,6 @@ definitions:
         type: integer
       memory_used_bytes:
         type: integer
-      network_rx_bytes:
-        type: integer
-      network_tx_bytes:
-        type: integer
       storage_total_bytes:
         type: integer
       storage_used_bytes:
@@ -2096,10 +2092,6 @@ definitions:
       bytes_received:
         description: sum(request_length)
         type: integer
-      network_rx_bytes:
-        type: integer
-      network_tx_bytes:
-        type: integer
       reported_nodes:
         type: integer
     type: object
@@ -2128,10 +2120,6 @@ definitions:
         type: integer
       memory_used_bytes:
         type: integer
-      network_rx_bytes:
-        type: integer
-      network_tx_bytes:
-        type: integer
       node_id:
         type: string
       openresty_connections:
@@ -2527,10 +2515,6 @@ definitions:
         type: integer
       memory_used_bytes:
         type: integer
-      network_rx_bytes:
-        type: integer
-      network_tx_bytes:
-        type: integer
       storage_total_bytes:
         type: integer
       storage_used_bytes: