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.

install/user/first-run/welcome.sh

@@ -1,5 +1,5 @@
 # Real newlines, not a literal \n: the card renders the body as it arrives, and
 # elides past three lines.
-omarchy-notification-send -u critical -g  "Learn Keybindings" \
-  $'Super + K for cheatsheet.\nSuper + Space for Omarchy Menu.' \
+omarchy-notification-send -u critical -g  "$(omarchy-text "Learn Keybindings")" \
+  "$(omarchy-text $'Super + K for cheatsheet.\nSuper + Space for Omarchy Menu.')" \
   --exec omarchy-menu-keybindings