Public API: event details, addresses, and change webhooks

The public API now returns more detail about your events. Events list their assigned staff, location details, and when they last changed. You can also request working windows for a date range of up to 31 days, and filter events by product or variant. Locations accept a structured address with street, city, region, postal code, country, phone, and coordinates. Changes to events and availability are now sent to your booking webhook URL.