feat: conditionally render room assignment field in participant edit form

src/Form/Service/CreateFieldStateProvider.php

@@ -263,8 +263,11 @@ class CreateFieldStateProvider extends AbstractFieldStateProvider
             'required' => new ApplicantCondition(),
         ];
 
-        // Render assignedRoomId field as static text when only one room type is selected (auto-assigned by RoomAssignmentService)
+        // Room assignment field:
+        // - Hidden until date of birth is provided (age determines room eligibility, e.g., Baby rooms)
+        // - Rendered as static text when only one room type is selected (auto-assigned by RoomAssignmentService)
         $this->fieldStateConditions['assignedRoomId'] = [
+            'hidden' => CompositeCondition::not($dateOfBirthProvidedCondition),
             'static_text' => new SingleRoomTypeCondition(),
         ];