Add Simplified Chinese as a system language

The installer asks for the language before the keyboard, and
Setup > Language (omarchy language en|zh) switches it later. Under
zh_CN the menu reads its labels from omarchy-menu.zh-cn.jsonc, the
shell from I18nZh.js through I18n.tr, and notifications are worded
by their sender through omarchy-text, which reads the same table.
User text is never translated.

shell/plugins/image-picker/ImagePicker.qml

@@ -126,7 +126,7 @@ Item {
 
   function currentLabel() {
     var path = currentPath()
-    if (!path) return filterText ? "No matches" : ""
+    if (!path) return filterText ? I18n.tr("No matches") : ""
 
     return labelForPath(path)
   }