fix(mana-events): cascade rate buckets when an event is unpublished

Add an ON DELETE CASCADE FK from rsvp_rate_buckets.token to
events_published.token. Without it, deleting a snapshot left orphaned
rate-limit rows behind, slowly leaking storage. Verified with a
direct SQL cascade test.

services/mana-events/src/db/schema/events.ts

@@ -74,7 +74,9 @@ export const publicRsvps = eventsSchema.table(
 export const rsvpRateBuckets = eventsSchema.table(
 	'rsvp_rate_buckets',
 	{
-		token: text('token').notNull(),
+		token: text('token')
+			.notNull()
+			.references(() => eventsPublished.token, { onDelete: 'cascade' }),
 		hourBucket: text('hour_bucket').notNull(), // YYYY-MM-DDTHH
 		count: integer('count').default(0).notNull(),
 	},