Fix Arabic RTL support: correct locale code and CSS syntax

- Rename ar-AR to ar-SA (valid BCP 47 code for Saudi Arabia)
- Fix missing dot in CSS selector: .news-section .news-header
- Add trailing newline to ar-SA.json

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

GUI/locales/ar-SA.json

@@ -254,4 +254,4 @@
     "installingGameFiles": "جاري تثبيت ملفات اللعبة...",
     "installComplete": "اكتمل التثبيت!"
   }
-}
+}