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/reminders/ReminderFlow.qml

@@ -29,7 +29,7 @@ Item {
   property int headerHeight: Math.max(Style.space(34), Style.font.title + Style.spacing.controlPaddingY * 2)
   property int cardWidth: Math.min(Style.space(300), panel.width - Style.gapsOut * 2)
   property int cardHeight: Math.min(contentMargin * 2 + headerHeight, panel.height - Style.gapsOut * 2)
-  readonly property string promptText: root.step === "message" ? "Reminder message" : "Remind in minutes"
+  readonly property string promptText: root.step === "message" ? I18n.tr("Reminder message") : I18n.tr("Remind in minutes")
 
   function open(payloadJson) {
     var payload = ({})
@@ -75,7 +75,7 @@ Item {
       }
 
       if (!nextMinutes) {
-        Quickshell.execDetached([root.omarchyPath + "/bin/omarchy-notification-send", "Invalid reminder", "Enter the number of minutes"])
+        Quickshell.execDetached([root.omarchyPath + "/bin/omarchy-notification-send", I18n.tr("Invalid reminder"), I18n.tr("Enter the number of minutes")])
         return
       }