chore: fix phpstan errors

src/Form/DataTransformer/RoomSelectionToIdTransformer.php

@@ -16,12 +16,12 @@ use Symfony\Component\Form\Exception\TransformationFailedException;
  * the full object (including price) via choiceData while the form binds
  * the scalar ID to the participant's assignedRoomId property.
  *
- * @implements DataTransformerInterface<int|null, RoomSelectionDto|null>
+ * @implements DataTransformerInterface<mixed, mixed>
  */
 class RoomSelectionToIdTransformer implements DataTransformerInterface
 {
     /**
-     * @param RoomSelectionDto[] $roomSelections Available room selections for reverse lookup
+     * @param array<RoomSelectionDto> $roomSelections Available room selections for reverse lookup
      */
     public function __construct(
         private readonly array $roomSelections,
@@ -29,11 +29,8 @@ class RoomSelectionToIdTransformer implements DataTransformerInterface
     }
 
     /**
-     * Transforms an integer room ID to a RoomSelectionDto for form display.
-     *
-     * @param int|null $value The room ID from the model
-     *
-     * @return RoomSelectionDto|null The matching RoomSelectionDto or null
+     * Converts the persisted room id from the model into the matching
+     * RoomSelectionDto so the form can render labels and pricing details.
      */
     public function transform(mixed $value): ?RoomSelectionDto
     {
@@ -51,29 +48,28 @@ class RoomSelectionToIdTransformer implements DataTransformerInterface
     }
 
     /**
-     * Transforms a RoomSelectionDto back to an integer room ID for the model.
+     * Converts the submitted choice value back into the model's integer room id.
      *
-     * @param RoomSelectionDto|null $value The selected RoomSelectionDto from the form
-     *
-     * @return int|null The room ID or null
-     *
-     * @throws TransformationFailedException If an unexpected value type is received
+     * ChoiceType submits the selected room id as a scalar, so this method accepts
+     * an empty value, an int, or a digit-only string and rejects everything else.
      */
     public function reverseTransform(mixed $value): ?int
     {
-        if (null === $value) {
+        if (null === $value || '' === $value) {
             return null;
         }
 
-        if ($value instanceof RoomSelectionDto) {
-            return $value->id;
+        if (is_int($value)) {
+            return $value;
         }
 
-        // Handle case where form submits scalar ID directly
-        if (is_int($value) || is_string($value)) {
+        if (is_string($value) && ctype_digit($value)) {
             return (int) $value;
         }
 
-        throw new TransformationFailedException(sprintf('Expected RoomSelectionDto, int, or null, got %s', get_debug_type($value)));
+        throw new TransformationFailedException(sprintf(
+            'Invalid room id value: %s',
+            get_debug_type($value)
+        ));
     }
 }