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>

tests/Unit/Policy/PolicyValueObjectsTest.php

@@ -0,0 +1,85 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Tests\Unit\Policy;
+
+use Unsupervised\Schedular\Policy\Policy;
+use Unsupervised\Schedular\Policy\PolicyAcceptance;
+use Unsupervised\Schedular\Policy\PolicyVersion;
+use Unsupervised\Schedular\Tests\Unit\TestCase;
+
+class PolicyValueObjectsTest extends TestCase
+{
+    public function testPolicyFromRowAndToArray(): void
+    {
+        $policy = Policy::fromRow((object) [
+            'id'                 => '4',
+            'title'              => 'Cancellation',
+            'slug'               => 'cancellation',
+            'current_version_id' => '9',
+        ]);
+
+        self::assertSame(4, $policy->id);
+        self::assertSame('cancellation', $policy->slug);
+        self::assertSame(9, $policy->currentVersionId);
+        self::assertArrayHasKey('current_version_id', $policy->toArray());
+    }
+
+    public function testPolicyHandlesNullCurrentVersion(): void
+    {
+        $policy = Policy::fromRow((object) [
+            'id'                 => '4',
+            'title'              => 'Cancellation',
+            'slug'               => 'cancellation',
+            'current_version_id' => null,
+        ]);
+
+        self::assertNull($policy->currentVersionId);
+    }
+
+    public function testPolicyVersionFromRowAndStatusHelper(): void
+    {
+        $version = PolicyVersion::fromRow((object) [
+            'id'             => '9',
+            'policy_id'      => '4',
+            'version_number' => '2',
+            'body'           => '<p>Policy</p>',
+            'status'         => PolicyVersion::STATUS_PUBLISHED,
+            'published_at'   => '2026-06-01 10:00:00',
+        ]);
+
+        self::assertSame(9, $version->id);
+        self::assertSame(2, $version->versionNumber);
+        self::assertTrue($version->isPublished());
+        self::assertSame('2026-06-01 10:00:00', $version->publishedAt);
+    }
+
+    public function testPolicyVersionDefaultsToDraft(): void
+    {
+        $version = new PolicyVersion(4, 1);
+
+        self::assertSame(PolicyVersion::STATUS_DRAFT, $version->status);
+        self::assertFalse($version->isPublished());
+        self::assertNull($version->publishedAt);
+        self::assertContains(PolicyVersion::STATUS_ARCHIVED, PolicyVersion::VALID_STATUSES);
+    }
+
+    public function testPolicyAcceptanceFromRowAndToArray(): void
+    {
+        $acceptance = PolicyAcceptance::fromRow((object) [
+            'id'                => '1',
+            'policy_version_id' => '9',
+            'student_id'        => '5',
+            'registration_type' => PolicyAcceptance::REG_LESSON,
+            'registration_id'   => '12',
+            'accepted_at'       => '2026-06-02 09:00:00',
+            'ip_address'        => '203.0.113.7',
+        ]);
+
+        self::assertSame(9, $acceptance->policyVersionId);
+        self::assertSame(PolicyAcceptance::REG_LESSON, $acceptance->registrationType);
+        self::assertSame('203.0.113.7', $acceptance->ipAddress);
+        self::assertArrayHasKey('policy_version_id', $acceptance->toArray());
+        self::assertContains(PolicyAcceptance::REG_ENROLLMENT, PolicyAcceptance::VALID_REGISTRATION_TYPES);
+    }
+}