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 <[email protected]>

src/Policy/PolicyAcceptance.php

@@ -0,0 +1,56 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Policy;
+
+class PolicyAcceptance {
+
+	public const REG_LESSON     = 'lesson';
+	public const REG_ENROLLMENT = 'enrollment';
+
+	/**
+	 * Polymorphic registration targets an acceptance can attach to.
+	 *
+	 * @var list<string>
+	 */
+	public const VALID_REGISTRATION_TYPES = [ self::REG_LESSON, self::REG_ENROLLMENT ];
+
+	public function __construct(
+		public readonly int $policyVersionId,
+		public readonly int $studentId,
+		public readonly string $registrationType,
+		public readonly int $registrationId,
+		public readonly ?string $ipAddress = null,
+		public readonly ?string $acceptedAt = null,
+		public readonly ?int $id = null,
+	) {}
+
+	public static function fromRow( object $row ): self {
+		return new self(
+			policyVersionId:  (int) $row->policy_version_id,
+			studentId:        (int) $row->student_id,
+			registrationType: $row->registration_type,
+			registrationId:   (int) $row->registration_id,
+			ipAddress:        $row->ip_address,
+			acceptedAt:       $row->accepted_at,
+			id:               (int) $row->id,
+		);
+	}
+
+	/**
+	 * Returns a plain array representation of the acceptance.
+	 *
+	 * @return array<string, mixed>
+	 */
+	public function toArray(): array {
+		return [
+			'id'                => $this->id,
+			'policy_version_id' => $this->policyVersionId,
+			'student_id'        => $this->studentId,
+			'registration_type' => $this->registrationType,
+			'registration_id'   => $this->registrationId,
+			'ip_address'        => $this->ipAddress,
+			'accepted_at'       => $this->acceptedAt,
+		];
+	}
+}