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.

bin/omarchy-system-reboot

@@ -8,7 +8,7 @@
 # scope cannot terminate it before it runs.
 systemd-run --user --collect --quiet --on-active="2s" --timer-property=AccuracySec=100ms systemctl reboot --no-wall || exit 1
 
-omarchy-osd -i reboot -m "Rebooting" -d 5000
+omarchy-osd -i reboot -m "$(omarchy-text "Rebooting")" -d 5000
 
 omarchy-state clear re*-required