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/polkit/PolkitAgent.qml

@@ -79,7 +79,7 @@ Item {
     var flow = polkitAgent.flow
     if (!flow) return
 
-    currentMessage = String(flow.message || "Authentication is needed...")
+    currentMessage = String(flow.message || I18n.tr("Authentication is needed..."))
     currentPrompt = String(flow.inputPrompt || "")
     currentSupplementary = String(flow.supplementaryMessage || "")
     responseRequired = !!flow.isResponseRequired
@@ -337,7 +337,7 @@ Item {
             anchors.left: parent.left
             anchors.right: parent.right
             anchors.verticalCenter: parent.verticalCenter
-            text: root.errorFlash ? "Wrong" : (root.submitted ? "Checking..." : "Enter password")
+            text: root.errorFlash ? I18n.tr("Wrong") : (root.submitted ? I18n.tr("Checking...") : I18n.tr("Enter password"))
             color: root.errorFlash ? Commons.Color.polkit.textError : root.foreground
             opacity: root.errorFlash ? 1 : 0.36
             font.family: root.fontFamily