Introduces a CF Queue binding (kk-email-queue) to decouple email
delivery from request handlers, preventing slow responses and
providing automatic retries. All send*Email calls now go through
the queue when the binding is available, with direct-send fallbacks
for local dev. Reminder fan-outs mark DB rows optimistically before
enqueueing to prevent re-enqueue on subsequent cron ticks.
Add management tokens to registrations allowing users to view, edit, and
cancel their registration via a unique URL. Implement email
notifications
for confirmations, updates, and cancellations using nodemailer. Simplify
art forms grid from 6 to 4 items and remove trajectory links. Translate
footer links to Dutch and fix matzah spelling in info section.
