docs: add inline documentation where missing

src/Validator/Constraints/RoomSelectionValidator.php

@@ -10,6 +10,12 @@ use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintValidator;
 use Symfony\Component\Validator\Exception\UnexpectedTypeException;
 
+/**
+ * Validates room selection business rules for bookings.
+ *
+ * Enforces that at least one room is selected and that baby rooms (BABY code)
+ * are only booked in combination with regular rooms, not standalone.
+ */
 class RoomSelectionValidator extends ConstraintValidator
 {
     public function validate(mixed $value, Constraint $constraint): void