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/PolicyController.php

@@ -0,0 +1,69 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Policy;
+
+use Unsupervised\Schedular\Auth\RoleManager;
+
+class PolicyController {
+
+	public function __construct(
+		private PolicyRepository $policies,
+		private PolicyVersionRepository $versions,
+		private PolicyService $service,
+	) {}
+
+	public function renderPage(): void {
+		if ( ! current_user_can( RoleManager::CAP_MANAGE_POLICIES ) ) {
+			wp_die( esc_html__( 'You do not have permission to manage policies.', 'unsupervised-schedular' ) );
+		}
+
+		if ( isset( $_POST['usc_action'] ) && check_admin_referer( 'usc_policy_action' ) ) {
+			$this->handleFormAction();
+		}
+
+		// phpcs:ignore WordPress.Security.NonceVerification.Recommended -- read-only policy selector.
+		$policyId       = absint( $_GET['policy_id'] ?? 0 );
+		$policyList     = $this->policies->findAll();
+		$selectedPolicy = $policyId > 0 ? $this->policies->findById( $policyId ) : null;
+		$policyVersions = null !== $selectedPolicy ? $this->versions->findByPolicy( (int) $selectedPolicy->id ) : null;
+
+		include USC_PLUGIN_DIR . 'templates/admin/policies.php';
+	}
+
+	private function handleFormAction(): void {
+		// Nonce is verified by the caller (renderPage) before this method runs.
+		// phpcs:disable WordPress.Security.NonceVerification.Missing
+		$action = sanitize_key( wp_unslash( $_POST['usc_action'] ?? '' ) );
+
+		if ( 'create_policy' === $action ) {
+			$title   = sanitize_text_field( wp_unslash( $_POST['title'] ?? '' ) );
+			$slugRaw = sanitize_text_field( wp_unslash( $_POST['slug'] ?? '' ) );
+			$slug    = sanitize_title( '' !== $slugRaw ? $slugRaw : $title );
+
+			if ( '' !== $title && '' !== $slug && null === $this->policies->findBySlug( $slug ) ) {
+				$this->service->createPolicy( $title, $slug );
+			}
+
+			return;
+		}
+
+		$policyId = absint( $_POST['policy_id'] ?? 0 );
+		if ( $policyId <= 0 || null === $this->policies->findById( $policyId ) ) {
+			return;
+		}
+
+		if ( 'add_version' === $action ) {
+			$body = wp_kses_post( wp_unslash( $_POST['body'] ?? '' ) );
+			$this->service->addDraftVersion( $policyId, $body );
+		}
+
+		if ( 'publish_version' === $action ) {
+			$versionId = absint( $_POST['version_id'] ?? 0 );
+			if ( $versionId > 0 ) {
+				$this->service->publishVersion( $policyId, $versionId );
+			}
+		}
+		// phpcs:enable WordPress.Security.NonceVerification.Missing
+	}
+}