Restructure src/ and tests/ from package-by-type to package-by-domain

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>

memory/MEMORY.md

@@ -2,3 +2,4 @@
 
 - [Project: unsupervised-schedular](project_schedular.md) — WordPress lesson scheduling plugin; initial scaffold created March 2026
 - [Feedback: Brain\Monkey testing patterns](feedback_brainmonkey.md) — specific API quirks discovered during test setup
+- [Feedback: Package-by-domain architecture](feedback_architecture.md) — all new code must be organised by domain, never by type

memory/feedback_architecture.md

@@ -0,0 +1,16 @@
+---
+name: Package-by-domain architecture
+description: New features must be organised as domain packages, not by type (no Admin/, Api/, Data/ etc.)
+type: feedback
+---
+
+Always organise code package-by-domain, not package-by-type.
+
+**Why:** User explicitly requested the restructure on 2026-03-30. Package-by-type (Admin/, Api/, Data/, Frontend/, Model/, Roles/) was the initial scaffold but was replaced before any real features shipped.
+
+**How to apply:**
+- New domain → new directory under `src/<Domain>/` (e.g. `src/Availability/`, `src/Booking/`, `src/Auth/`)
+- All classes for a domain (value objects, repositories, admin controllers, REST endpoints, shortcode pages) live inside that directory under the sub-namespace `Unsupervised\Schedular\<Domain>\`
+- Cross-cutting wiring that glues domains together (Plugin, AdminMenu, RestRegistrar, ShortcodeRegistrar, Schema) lives at `src/` root with namespace `Unsupervised\Schedular\`
+- Tests mirror the domain structure: `tests/Unit/<Domain>/`
+- Never create `src/Admin/`, `src/Api/`, `src/Data/`, `src/Frontend/`, `src/Model/`, or `src/Roles/` directories

memory/project_schedular.md

@@ -15,5 +15,6 @@ WordPress plugin for instructor/student lesson scheduling. Full scaffold created
 - REST API (`us-scheduler/v1`) for all front-end interactions; templates are minimal shell divs, JS (vanilla) takes over
 - Instructors use wp-admin login; students use front-end `[us_student_login]` shortcode calling `wp_signon()`
 - PSR-4 namespace `Unsupervised\Schedular\` from `src/`
+- **Package-by-domain architecture** (restructured 2026-03-30): `src/Availability/`, `src/Booking/`, `src/Auth/` — each domain contains its value object, repository, controller, REST endpoint, and any shortcode pages. Cross-cutting wiring (Plugin, AdminMenu, RestRegistrar, ShortcodeRegistrar, Schema) lives at `src/` root. Tests mirror the domain structure under `tests/Unit/<Domain>/`.
 
-**How to apply:** When adding features, follow the docs/features/ + src/ + tests/Unit/ pattern. Always run `composer test` after changes.
+**How to apply:** When adding features, create a domain package under `src/<Domain>/` with all related classes, mirror it in `tests/Unit/<Domain>/`, write a feature doc in `docs/features/`, then run `composer test`.