feat(registrations): revenue and average order cards on the Registration page

[harshtandiya]

What changed

The Registration page gets Revenue and Average order cards above Ticket Types. get_event_ticket_types now returns revenue: one row per currency with collected, refunded, bookings and tickets. Rows come from paid, submitted bookings with a non-zero total. The gate is the existing ensure_event_team_access, so only team members see it.

• Offline bookings awaiting approval are already submitted (docstatus=1), so payment_status="Paid" is the filter that keeps them out of revenue. Free bookings are left out too, so they don't drag down the average.
• Ticket counts are a separate query. Joining tickets into the sum query would multiply each booking's total by its ticket count.
• Currencies are never added together. The currency with the most bookings is the reading; the others go in the Revenue caption ("+ $1,815"), next to the refunded amount.
• Revenue = collected − refunded. Average order = collected ÷ bookings, with "N tickets per booking" under it. No cards on an event with no paid bookings.

Separate commit: price rows in the ticket type drawer line up. A locked currency row has no remove button, so it now keeps that button's width. Rows are also 8px apart instead of 2px. PerkList shares the component.

Not changed: a booking cancelled without a refund drops out of revenue (docstatus=2) even though the money was kept. Event Booking.event and Event Ticket.booking have no index, so these queries scan both tables, like the existing tickets_sold_by_type already does. Indexing is left for a follow-up.

Demo

Testing

Checks: test_ticket_types (9, 4 new in TestRegistrationRevenue) green on testbuzz. Removing the paid/free/cancelled filters makes the new tests fail. Typecheck and pre-commit clean. Not run: E2E, other test modules.

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