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.

migrations_fork.py

@@ -156,3 +156,32 @@ async def m003_event_nostr_publish_pending(db):
         "ALTER TABLE events.events "
         "ADD COLUMN nostr_publish_pending BOOLEAN NOT NULL DEFAULT FALSE",
     )
+
+
+async def m004_event_nostr_published_wave(db):
+    """
+    Add `events.nostr_published_wave_id` — which ticket wave the last
+    successful NIP-52 publish advertised.
+
+    Since upstream v1.6.8 price and inventory live on time-boxed waves, so
+    what a calendar event should advertise changes at a *date* boundary.
+    Every republish we have is sale-driven, and no sale happens at
+    midnight when early bird ends — so without this the relay keeps
+    serving the closed wave's price until the next ticket sells
+    (aiolabs/events#61).
+
+    Recording the advertised wave makes that drift detectable with the
+    machinery already in place: the reconciliation sweep compares this
+    against the wave that would be advertised now and sets
+    `nostr_publish_pending`, reusing the existing retry path rather than
+    adding a scheduler.
+
+    NULL on existing rows means "never published, or published before this
+    column existed". The sweep treats NULL as "no evidence of drift" and
+    leaves it alone, so an upgrade does not stampede the signer with a
+    full-table republish; the first ordinary publish fills it in.
+    """
+    await _alter_add_column_safe(
+        db,
+        "ALTER TABLE events.events ADD COLUMN nostr_published_wave_id TEXT",
+    )