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/Models/CrowdList.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Models;
 
+use App\Enums\CrowdListType;
 use Illuminate\Database\Eloquent\Concerns\HasUlids;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
@@ -28,6 +29,7 @@ final class CrowdList extends Model
     protected function casts(): array
     {
         return [
+            'type' => CrowdListType::class,
             'auto_approve' => 'boolean',
             'max_persons' => 'integer',
         ];