All classes are now organised by domain (Availability, Booking, Auth).
Each domain package contains its value object, repository, admin controller,
REST endpoint, and any shortcode pages under a matching sub-namespace.
Cross-cutting wiring (Plugin, AdminMenu, RestRegistrar, ShortcodeRegistrar,
Schema) lives at src/ root. Tests mirror the domain structure.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
