fix: UI 语义区分会话总量与日月累计 + 修复 onVisibleChanged 重复

弹窗'流量总计'改为'本次会话'，明确是本次 dde-shell 运行期间累计；
流量统计窗口'按接口累计'改为'今日累计/本月累计'，明确是跨重启持久化。
修复 TrafficStatsWindow onVisibleChanged 重复设置导致插件加载失败

translations/jnetapplet_zh_CN.ts

@@ -78,8 +78,8 @@
     </message>
     <message>
         <location filename="../package/components/NetworkPopup.qml" line="427"/>
-        <source>Total</source>
-        <translation>流量总计</translation>
+        <source>Session Total</source>
+        <translation>本次会话</translation>
     </message>
     <message>
         <location filename="../package/components/NetworkPopup.qml" line="474"/>
@@ -295,8 +295,13 @@
     </message>
     <message>
         <location filename="../package/components/TrafficStatsWindow.qml" line="202"/>
-        <source>Accumulated by interface</source>
-        <translation>按接口累计</translation>
+        <source>Today accumulated</source>
+        <translation>今日累计</translation>
+    </message>
+    <message>
+        <location filename="../package/components/TrafficStatsWindow.qml" line="214"/>
+        <source>This month accumulated</source>
+        <translation>本月累计</translation>
     </message>
     <message>
         <location filename="../package/components/TrafficStatsWindow.qml" line="218"/>