Add placeholder for package progress#4818

Package emails can include all booked appointments via the %package_appointments_details% placeholder, but there’s no placeholder for “used/total” (like 2/10) or “remaining” credits.

Package usage (e.g. 1/3) is visible in the back-end Packages list and in the customer’s Packages tab in the Customer Panel, but not in notifications/calendar.

Google/Outlook event titles/descriptions can use existing notification placeholders, but none expose package progress.

It would be awesome to have a placeholder that shows package progress/credits to be added in confirmation emails and on calendar appointment details.