fix(stats): finalize snapshots on the verse-day window

A verse date is a player's local calendar day, spanning D-1 10:00Z
(UTC+14) through D+1 12:00Z (UTC-12). The old UTC end-of-day cutoff both
dropped late-night finishes in negative timezones and could persist a
partial day.

- Scope snapshot loads by the verse date column; use completedBefore only
  to pin an in-progress point-in-time build.
- Gate persistence on isDayClosed (D+1 12:00Z); open days are computed
  live and never written.
- Build the cron snapshot for latestClosedDate instead of EST yesterday,
  and read the same date for the community page.
- Add all-time best single day to snapshot totals.
- Bump PAYLOAD_SCHEMA_VERSION to 4 and extend snapshot/window tests.

src/routes/api/cron/build-stats/+server.ts

@@ -1,13 +1,13 @@
 import { json } from '@sveltejs/kit';
 import type { RequestHandler } from './$types';
-import { addDays } from '$lib/server/stats/dates';
+import { latestClosedDate } from '$lib/server/stats/dates';
 import { buildSnapshot } from '$lib/server/stats/snapshot';
 import { sendDigest } from '$lib/server/stats/digest';
 
 /**
  * Daily snapshot build trigger. Protected by `Authorization: Bearer $CRON_SECRET`
- * (same pattern as `/api/send-daily-verse`). Builds yesterday in `America/New_York`
- * and then sends the digest.
+ * (same pattern as `/api/send-daily-verse`). Builds the most recent date whose
+ * global data window has closed, then sends the digest.
  */
 export const POST: RequestHandler = async ({ request }) => {
 	const cronSecret = Bun.env.CRON_SECRET;
@@ -16,10 +16,9 @@ export const POST: RequestHandler = async ({ request }) => {
 		return json({ error: 'Unauthorized' }, { status: 401 });
 	}
 
-	const todayEst = new Date().toLocaleDateString('en-CA', { timeZone: 'America/New_York' });
-	const yesterday = addDays(todayEst, -1);
+	const date = latestClosedDate();
 
-	const { snapshot } = await buildSnapshot(yesterday, {
+	const { snapshot } = await buildSnapshot(date, {
 		kind: 'scheduled',
 		replace: true
 	});
@@ -27,5 +26,5 @@ export const POST: RequestHandler = async ({ request }) => {
 	// Digest failure must never fail the build.
 	await sendDigest(snapshot.payload);
 
-	return json({ ok: true, date: yesterday, buildKind: 'scheduled' });
+	return json({ ok: true, date, buildKind: 'scheduled' });
 };