Add Policies domain (drafting, versioning, tracked acceptance)

Implements #6: studio admins draft, version, and publish policies; the
public registration gate reads the current published version of each, and
acceptance is recorded against the exact version so a new version must be
re-accepted at the next booking.

- src/Policy/: Policy, PolicyVersion, PolicyAcceptance value objects;
  PolicyRepository, PolicyVersionRepository, AcceptanceRepository;
  PolicyService (orchestrates create/add-draft/publish across the policies
  and versions tables); PolicyEndpoint (REST); PolicyController +
  templates/admin/policies.php (Policies admin menu, manage_policies)
- us_policies, us_policy_versions, us_policy_acceptances tables in Schema
- REST: public GET /policies (current published versions); manage_policies
  for create, add version, edit draft, and publish
- Wiring in Plugin, RestRegistrar, AdminMenu

AcceptanceRepository is built now and consumed by the booking/enrolment
gate in #3/#4.

Also bump PHPStan to --memory-limit=1G in the composer lint script; the
default 128M now crashes the analysis as the codebase has grown.

Tests: tests/Unit/Policy/ (value objects, repositories, service).
composer test (90 total), cs, and PHPStan level 6 all pass.

Refs #6

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/AdminMenu.php

@@ -10,6 +10,10 @@ use Unsupervised\Schedular\Booking\BookingRepository;
 use Unsupervised\Schedular\Booking\LessonController;
 use Unsupervised\Schedular\Offering\OfferingController;
 use Unsupervised\Schedular\Offering\OfferingRepository;
+use Unsupervised\Schedular\Policy\PolicyController;
+use Unsupervised\Schedular\Policy\PolicyRepository;
+use Unsupervised\Schedular\Policy\PolicyService;
+use Unsupervised\Schedular\Policy\PolicyVersionRepository;
 use Unsupervised\Schedular\Registration\QuestionController;
 use Unsupervised\Schedular\Registration\QuestionRepository;
 
@@ -19,12 +23,14 @@ class AdminMenu {
 	private LessonController $lessonController;
 	private OfferingController $offeringController;
 	private QuestionController $questionController;
+	private PolicyController $policyController;
 
-	public function __construct( AvailabilityRepository $availability, BookingRepository $bookings, OfferingRepository $offerings, QuestionRepository $questions ) {
+	public function __construct( AvailabilityRepository $availability, BookingRepository $bookings, OfferingRepository $offerings, QuestionRepository $questions, PolicyRepository $policies, PolicyVersionRepository $policyVersions, PolicyService $policyService ) {
 		$this->availabilityController = new AvailabilityController( $availability );
 		$this->lessonController       = new LessonController( $bookings );
 		$this->offeringController     = new OfferingController( $offerings );
 		$this->questionController     = new QuestionController( $questions, $offerings );
+		$this->policyController       = new PolicyController( $policies, $policyVersions, $policyService );
 	}
 
 	public function register(): void {
@@ -75,6 +81,17 @@ class AdminMenu {
 			[ $this->questionController, 'renderPage' ]
 		);
 
+		// Studio admin: draft, version, and publish policies.
+		add_menu_page(
+			__( 'Policies', 'unsupervised-schedular' ),
+			__( 'Policies', 'unsupervised-schedular' ),
+			RoleManager::CAP_MANAGE_POLICIES,
+			'us-policies',
+			[ $this->policyController, 'renderPage' ],
+			'dashicons-text-page',
+			34
+		);
+
 		// Instructor: view their upcoming lessons.
 		add_menu_page(
 			__( 'My Lessons', 'unsupervised-schedular' ),