fix(test): commit edge row so delete step sees it in its own session

The "Deleting a resource with edges is rejected" scenario was failing
because the ResourceEdgeModel row was flushed but never committed.
Since ResourceRepository.delete() obtains its own session from the
factory, the uncommitted edge was invisible and ResourceHasEdgesError
was never raised.

features/steps/resource_repository_steps.py

@@ -652,6 +652,7 @@ def step_parent_child_linked(context: Context, type_name: str) -> None:
     )
     session.add(edge)
     session.flush()
+    session.commit()
 
 
 @when("the parent resource is deleted")