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/lock/LockView.qml

@@ -25,7 +25,7 @@ Item {
   property string passwordText: ""
   property bool syncingPasswordText: false
 
-  readonly property string placeholderText: "Enter Password"
+  readonly property string placeholderText: I18n.tr("Enter Password")
   readonly property int fieldWidth: 381
   readonly property int fieldHeight: 67
   readonly property int outlineThickness: 3
@@ -223,7 +223,7 @@ Item {
       Text {
         textFormat: Text.PlainText
         anchors.fill: passwordInput
-        text: root.authenticatingPassword ? "Checking…" : (root.failureMessage.length > 0 ? root.failureMessage : root.placeholderText)
+        text: root.authenticatingPassword ? I18n.tr("Checking…") : (root.failureMessage.length > 0 ? root.failureMessage : root.placeholderText)
         visible: passwordInput.text.length === 0
         color: root.authenticatingPassword ? Commons.Color.lock.text : (root.failureMessage.length > 0 ? Commons.Color.lock.textError : Commons.Color.lock.placeholder)
         font.family: Style.font.family
@@ -266,7 +266,7 @@ Item {
       anchors.topMargin: 18
       anchors.horizontalCenter: inputField.horizontalCenter
       visible: root.fingerprintConfigured && root.fingerprintUnavailable
-      text: "Fingerprint reader unavailable"
+      text: I18n.tr("Fingerprint reader unavailable")
       color: Commons.Color.lock.textError
       font.family: Style.font.family
       font.pixelSize: Style.font.heading