Fix reservation ticket counters

[egorvaganov]

Summary

Fix reservation ticket counters displayed in the account reservations page.

Changes

• add valid_tickets_count
• add cancelled_tickets_count
• exclude pending/cancelled tickets from valid count
• update reservation template
• add pytest coverage for all counter scenarios

Tests

poetry run pytest tests/pytest/test_reservation_valid_tickets_count.py -v

[Nasjoe]

Hello!
Thank you so much for this PR!
It'll be really useful :)

I noticed a minor N+1 performance issue.
Do you want to look into this? (Probably using an annotation.) Or do you want us to handle it?
Thank you very much!

[egorvaganov]

Hi! Thanks for catching that 🙏

Fixed the N+1 by adding an annotation in MyAccount.my_reservations() (BaseBillet/views.py):

.annotate(
    annotated_valid_count=Count(
        'tickets', filter=Q(tickets__status__in=[Ticket.NOT_SCANNED, Ticket.SCANNED])
    ),
    annotated_cancelled_count=Count(
        'tickets', filter=Q(tickets__status=Ticket.CANCELED)
    ),
)

This computes both counts for all reservations in a single query instead of two queries per reservation.

I kept the existing Reservation.valid_tickets_count() / cancelled_tickets_count() methods on the model as-is, since they're still used elsewhere (single-object access, tests). I used different attribute names for the annotations (annotated_valid_count / annotated_cancelled_count) rather than reusing the method names, to avoid Django silently shadowing the methods on instances built from this queryset — that would otherwise make .valid_tickets_count() raise TypeError: 'int' object is not callable for any code still calling it as a method.

Also added a regression test that builds the same annotated queryset and asserts it matches the model methods' output on a mixed set of ticket statuses, so any future drift between the two would be caught by CI.

Updated reservations.html to use the annotated fields instead of calling the methods.

Let me know if you'd prefer a different approach!