feat(admin-center): implement organization calculation method settings

- Added functionality to update the organization's calculation method (hourly or man-days) in the Admin Center.
- Created a new component for managing the calculation method, including UI elements for selection and saving changes.
- Updated API service to handle the new endpoint for updating the calculation method.
- Enhanced localization files to support new keys related to the calculation method settings.
- Introduced a settings page to manage organization working days and hours alongside the calculation method.

worklenz-frontend/public/locales/de/admin-center/sidebar.json

@@ -4,5 +4,6 @@
   "teams": "Teams",
   "billing": "Abrechnung",
   "projects": "Projekte",
+  "settings": "Einstellungen",
   "adminCenter": "Admin-Center"
 }