Adds the Arabic catalog to the dashboard, registers it in the locale list
and picker, and flips the document direction to RTL when Arabic is active.
Introduces a `defineLocale` merge helper (mirroring the desktop app) so the
Arabic catalog can be a partial override that falls back to English for any
untranslated key instead of hand-porting every future string.
Co-authored-by: morolab <ahmedmoro@gmail.com>