`CreateTicket` no longer rejects `user_id` together with `name`/`email`
(the exclusion was a fork-only dispatch convenience from dfabcb8; nothing
needed it). `crud.create_ticket` stops blanking name/email when a user_id
is present, so logged-in webapp buyers can have their ticket emailed —
until now `_send_ticket_notification` short-circuited on the empty
address for every app purchase.
New optional `frontend_url` (absolute http(s) root, no query/fragment/..,
trailing slash stripped) lets a buyer-side client name the app the buyer
should be returned to and linked into from the ticket email; the origin
allow-list lives in views_api.
Also folds in the pending black reflow of migrations_fork.py.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EYwoAkZZmXMMmaBp4WGUBo
