feat(nostr): publish the active ticket wave, not the roll-up

Since upstream v1.6.8 price, currency and inventory belong to time-boxed
ticket waves, and the event-level fields `sync_event_ticket_waves`
derives are the PRIMARY wave's price/currency and the SUM of every
wave's stock. The NIP-52 publisher read those, so as soon as an
organiser created a second wave the public card would advertise the
early-bird price after early bird closed and count stock in waves that
had not opened. Refs #61.

`build_nip52_event` now describes the wave a buyer can actually buy
from:

- several waves can be open at once, and a publisher has no one to ask
  which one the buyer wants (the purchase endpoint errors with "Please
  select a ticket wave"), so it advertises the CHEAPEST open wave — the
  price a buyer is able to obtain. Deviation recorded in
  docs/upstream-candidates.md.
- with no open wave, `tickets_available` is 0 and never omitted:
  omission used to mean "unlimited", which #34/#62 removed as a concept.
- `tickets_payment_methods` is scoped to the advertised wave too. It was
  derived from `event.allow_fiat` — the primary wave's — so it could
  offer a fiat rail while `tickets_allow_fiat` was absent and the
  purchase endpoint would refuse it. They are the same fact and now come
  from the same place.

Wave boundaries are time-driven, and every republish we have is
sale-driven, so nothing fires when early bird ends at midnight. Rather
than add a scheduler, a publish records which wave it advertised
(`nostr_published_wave_id`, m004) and the reconciliation sweep compares
that against the wave that would be advertised now, setting
`nostr_publish_pending` on a mismatch — reusing the existing retry path.
NULL means "never published", which the sweep leaves alone so an upgrade
does not republish the whole table on first boot.

The selection rule lives in `models.advertised_ticket_wave` so the
publisher and the drift detector cannot disagree about what is on the
relay.

17 new tests; 114 pass. ruff, black, prettier clean; mypy error set
still identical to HEAD's baseline.

__init__.py

@@ -139,12 +139,22 @@ def events_start():
         Quiet by design: on a healthy instance the query returns nothing
         and this logs nothing. It only speaks up when there is drift.
         """
-        from .crud import get_events_pending_republish
+        from .crud import flag_wave_transitions, get_events_pending_republish
         from .nostr_hooks import publish_or_delete_nostr_event
 
         await asyncio.sleep(REPUBLISH_SWEEP_FIRST_DELAY)
         while True:
             try:
+                # Wave boundaries are time-driven, so nothing else flags
+                # them. Done here rather than on a timer of its own: the
+                # boundary is day-granular, so one sweep interval of
+                # staleness is immaterial (aiolabs/events#61).
+                moved = await flag_wave_transitions()
+                if moved:
+                    logger.info(
+                        f"[EVENTS] Republish sweep: {moved} event(s) changed "
+                        f"ticket wave"
+                    )
                 pending = await get_events_pending_republish()
                 if pending:
                     total = len(pending)