feat: replace board service placeholder to avoid duplicate entries

src/Form/AccommodationStep2Type.php

@@ -40,8 +40,7 @@ class AccommodationStep2Type extends AbstractType
                 'choices' => $options['board_service_choices'],
                 'expanded' => true,
                 'multiple' => false,
-                'required' => false,
-                'placeholder' => 'Selbstversorgung',
+                'required' => true,
             ])
             ->add('selectedAdditionalServiceIds', ChoiceType::class, [
                 'label' => false,
@@ -65,11 +64,6 @@ class AccommodationStep2Type extends AbstractType
                 }
             }
 
-            // Board service rendered manually: empty string from the "Selbstversorgung" radio → null
-            if (isset($data['selectedBoardServiceId']) && '' === $data['selectedBoardServiceId']) {
-                unset($data['selectedBoardServiceId']);
-            }
-
             $event->setData($data);
         });
     }

src/Form/Model/AccommodationBookingDto.php

@@ -25,6 +25,7 @@ class AccommodationBookingDto
     #[Assert\PositiveOrZero(message: 'invalid', groups: ['step_3'])]
     public int $childrenCount = 0;
 
+    #[Assert\NotNull(message: 'required', groups: ['step_2'])]
     public ?int $selectedBoardServiceId = null;
 
     /** @var list<int>*/