Plan:
1.  **Bilingual Admin Panel:** Updated the entire Admin Panel (`admin.php`, `admin_documents.php`, `admin_categories.php`, etc.) to support both English and Arabic.
2.  **Language Switcher:** Added a language toggle button to the admin sidebar in `includes/admin_layout.php`.
3.  **RTL Support:** Configured `includes/admin_layout.php` to automatically switch to Right-to-Left (RTL) layout and load Bootstrap RTL when Arabic is selected.
4.  **Translations:** Added comprehensive translation keys to `includes/library.php` covering dashboard metrics, tables, forms, buttons, and confirmation dialogs.

Changed (if any):
*   `includes/library.php`: Added translation keys for admin panel terms.
*   `includes/admin_layout.php`: Implemented language switcher and RTL logic.
*   `admin.php`: Localized the Dashboard.
*   `admin_documents.php`: Localized the Material Entry page.
*   `admin_categories.php`: Localized the Categories management page.
*   `admin_subcategories.php`: Localized the Subcategories management page.
*   `admin_types.php`: Localized the Types management page.

Notes:
*   **Try it out:** Go to the Admin Panel and click the "العربية" button in the sidebar to switch the entire interface to Arabic.
*   **Reminder:** Click **Save** in the editor to apply these changes.

Next: Verify the Arabic layout and translations in the Admin Panel!