feat: add notifications module with bell UI, event listeners, and cleanup job

In-app notification system with topbar bell icon, dropdown panel,
mark-as-read/dismiss actions, and scheduled cleanup of old read
notifications. Includes event listeners for user.created and
user.deleted events, authorization policy, and full test coverage.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/notifications/lib/Module/Notifications/NotificationsAuthorizationPolicy.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace MintyPHP\Module\Notifications;
+
+use MintyPHP\Service\Access\AuthorizationDecision;
+use MintyPHP\Service\Access\AuthorizationPolicyInterface;
+
+final class NotificationsAuthorizationPolicy implements AuthorizationPolicyInterface
+{
+    public const ABILITY_VIEW = 'notifications.view';
+    public const PERMISSION_KEY = 'notifications.view';
+
+    public function supports(string $ability): bool
+    {
+        return $ability === self::ABILITY_VIEW;
+    }
+
+    public function authorize(string $ability, array $context = []): AuthorizationDecision
+    {
+        $actorUserId = (int) ($context['actor_user_id'] ?? 0);
+        if ($actorUserId <= 0) {
+            return AuthorizationDecision::deny(403, 'forbidden');
+        }
+
+        return AuthorizationDecision::allow();
+    }
+}