Calculates admin-specific URL for source resource, regardless of receipt audience.

Unlike source_url which uses the receipt's audience to determine the URL path, this calculation always uses audience: :admin. This is useful for admin dashboards that need to link to admin views regardless of who the notification was sent to.

Configuration

config :ash_dispatch, url_builder: MyApp.UrlBuilder

The UrlBuilder must implement build_resource_url/3 with support for audience: :admin.