feat(workspace): add workbench layout and traffic totals

Rework the default /workspace layout into a three-column view
with a left-side Workbench, centered terminal, and right-side
status monitor.

Add a new Workbench pane that groups file manager, command
history, and editor into tabs while preserving panel state.
Extend server status data to expose cumulative network upload
and download totals since boot, and show them in the monitor.

Include a lightweight migration for the old default layout and
update related locale strings, pane metadata, and knowledge
base records.

packages/frontend/src/locales/zh-CN.json

@@ -583,6 +583,9 @@
     "swapLabel": "Swap:",
     "diskLabel": "磁盘:",
     "networkLabel": "网络",
+    "totalTrafficLabel": "开机累计流量",
+    "downloadLabel": "下行",
+    "uploadLabel": "上行",
     "notAvailable": "N/A",
     "bytesPerSecond": "B/s",
     "kiloBytesPerSecond": "KB/s",
@@ -1254,10 +1257,11 @@
     "pane": {
       "connections": "连接列表",
       "terminal": "终端",
-      "commandBar": "命令栏",
-      "fileManager": "文件管理器",
-      "editor": "编辑器",
-      "statusMonitor": "状态监视器",
+        "commandBar": "命令栏",
+        "fileManager": "文件管理器",
+        "editor": "编辑器",
+        "workbench": "工作台",
+        "statusMonitor": "状态监视器",
       "commandHistory": "命令历史",
       "quickCommands": "快捷指令",
       "dockerManager": "Docker 管理器",
@@ -1266,14 +1270,28 @@
     "panes": {
       "suspendedSshSessions": "挂起会话管理器"
     },
-    "noActiveSession": {
-      "title": "无活动会话",
-      "message": "请先连接一个会话",
-      "fileManagerSidebar": "文件管理器需要活动会话",
-      "statusMonitorSidebar": "状态监视器需要活动会话"
-    }
-  },
-  "header": {
+      "noActiveSession": {
+        "title": "无活动会话",
+        "message": "请先连接一个会话",
+        "fileManagerSidebar": "文件管理器需要活动会话",
+        "statusMonitorSidebar": "状态监视器需要活动会话"
+      }
+    },
+    "workspace": {
+      "noActiveSession": "没有活动的会话",
+      "workbench": {
+        "title": "Workbench",
+        "label": "工作台",
+        "noSession": "未激活会话",
+        "fileManagerHint": "激活一个 SSH 会话后即可浏览远程文件。",
+        "tabs": {
+          "files": "文件",
+          "history": "历史命令",
+          "editor": "编辑器"
+        }
+      }
+    },
+    "header": {
     "hide": "隐藏",
     "show": "显示顶部导航"
   },