feat: remove room selection field entirely for single room type

addresses #869axcukn

src/Form/Service/CreateFieldStateProvider.php

@@ -205,9 +205,9 @@ class CreateFieldStateProvider extends AbstractFieldStateProvider
             'required' => new ApplicantCondition(),
         ];
 
-        // Make assignedRoomId readonly when only one room type is selected
+        // Hide assignedRoomId field when only one room type is selected (auto-assigned by RoomAssignmentService)
         $this->fieldStateConditions['assignedRoomId'] = [
-            'readonly' => new SingleRoomTypeCondition(),
+            'hidden' => new SingleRoomTypeCondition(),
         ];
 
         // Example field state conditions would be registered here