feat: make room selection fields read-only for single room type

src/Form/Service/ParticipantFieldOptionsProvider.php

@@ -84,7 +84,7 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
         // Room assignment field provider (only available for create workflow)
         $this->fieldOptionProviders['assignedRoomId'] = fn (BookingDtoInterface $bookingDto, int $participantIndex, array $options = []) => [
             'label' => 'Zimmer',
-            'placeholder' => 'Bitte wählen',
+            'placeholder' => 'Nicht zugeordnet',
             // Use factory to create context-aware choice loader that:
             // - Shows only available rooms for this participant
             // - Excludes rooms already assigned to other participants
@@ -96,6 +96,9 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
                     $participantIndex
                 )
                 : null,
+            // Make field read-only when only one room type is selected
+            // Room is auto-assigned, no user choice needed
+            'disabled' => $bookingDto instanceof BookingCreateDto && 1 === count($bookingDto->getSelectedRooms()),
         ];
 
         // Courses field provider - provides age-appropriate courses from travel data