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/Plugin.php

@@ -7,6 +7,9 @@ use Unsupervised\Schedular\Auth\RoleManager;
 use Unsupervised\Schedular\Availability\AvailabilityRepository;
 use Unsupervised\Schedular\Booking\BookingRepository;
 use Unsupervised\Schedular\Offering\OfferingRepository;
+use Unsupervised\Schedular\Policy\PolicyRepository;
+use Unsupervised\Schedular\Policy\PolicyService;
+use Unsupervised\Schedular\Policy\PolicyVersionRepository;
 use Unsupervised\Schedular\Registration\QuestionRepository;
 
 class Plugin {
@@ -15,14 +18,17 @@ class Plugin {
 		load_plugin_textdomain( 'unsupervised-schedular', false, dirname( plugin_basename( USC_PLUGIN_FILE ) ) . '/languages' );
 
 		global $wpdb;
-		$availability = new AvailabilityRepository( $wpdb );
-		$bookings     = new BookingRepository( $wpdb );
-		$offerings    = new OfferingRepository( $wpdb );
-		$questions    = new QuestionRepository( $wpdb );
+		$availability   = new AvailabilityRepository( $wpdb );
+		$bookings       = new BookingRepository( $wpdb );
+		$offerings      = new OfferingRepository( $wpdb );
+		$questions      = new QuestionRepository( $wpdb );
+		$policies       = new PolicyRepository( $wpdb );
+		$policyVersions = new PolicyVersionRepository( $wpdb );
+		$policyService  = new PolicyService( $policies, $policyVersions );
 
 		( new RoleManager() )->register();
-		( new AdminMenu( $availability, $bookings, $offerings, $questions ) )->register();
-		( new RestRegistrar( $availability, $bookings, $offerings, $questions ) )->register();
+		( new AdminMenu( $availability, $bookings, $offerings, $questions, $policies, $policyVersions, $policyService ) )->register();
+		( new RestRegistrar( $availability, $bookings, $offerings, $questions, $policies, $policyVersions, $policyService ) )->register();
 		( new ShortcodeRegistrar() )->register();
 	}
 }