fix: reset room assignments after updated selection if required

src/Controller/Booking/Create/Step2Controller.php

@@ -74,6 +74,9 @@ class Step2Controller extends AbstractController
             fn ($user, $participant) => $this->prepopulationService->prepopulateApplicantFromUser($user, $participant)
         );
 
+        // Validate room assignments against current selection (handles back-navigation from step 2 to step 1)
+        $this->roomAssignmentService->validateAndResetInvalidAssignments($bookingCreateDto);
+
         // Auto-assign rooms if needed
         $this->roomAssignmentService->assignRoomsIfNeeded($bookingCreateDto);