feat: crowd lists audit, enum, factory, service and tests

Audit and complete the Crowd Lists module:
- Add CrowdListType enum (internal/external) with proper casts
- Create CrowdListService for business logic (add/remove person,
  max_persons enforcement, auto_approve, activity logging)
- Create CrowdListFactory with Dutch names and states
- Create AddPersonToCrowdListRequest form request
- Fix FormRequests to use Rule::enum instead of hardcoded strings
- Fix CrowdListResource to use enum->value and add is_full field
- Refactor controller to be thin (delegates to service)
- Add eager loading for crowdType and recipientCompany
- Write 18 comprehensive tests (CRUD, auth, edge cases)
- Update API.md with request/response documentation

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

api/app/Enums/CrowdListType.php

@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums;
+
+enum CrowdListType: string
+{
+    case INTERNAL = 'internal';
+    case EXTERNAL = 'external';
+}