Get sales data

Returns the historical event_stats time series for a single event. Each snapshot row includes event-level aggregates (avg/median price, get-in price, listing fill rate) AND inline zone-level breakdowns for every zone in that snapshot. ## Billing rules | Scenario | Charged a pull? | |---|---| | First request for an event (no cursor, snapshots exist) | Yes - 1 pull | | Follow-up paginated page (cursor present) | No (continuation) | | Repeat first-page request, no new snapshot since last paid pull | No (freshness rule) | | Repeat first-page request, new snapshot logged in between | Yes - 1 pull | | Event has no event_stats rows yet | No (empty result, free) | The freshness rule means polling for "is there fresh data?" only costs when there's actually new data to consume. ## Pagination Cursor-based. The first page response includes `total_count` and `available_zones`; subsequent paginated pages omit them. Cursors expire after 1 hour.