The SnapshotsAPITestCreateUpdate test expects that PUT /api/snapshots/:name
with the same Name in the body returns a conflict error. The previous fix
added 'b.Name != name' guards to skip the duplicate check when the name
hasn't changed, but this broke the test which expects the old behavior:
any existing name (including the snapshot's own current name) should be
rejected as a duplicate.
Remove the 'b.Name != name' condition from both the pre-task validation
and the in-task duplicate check so the behavior matches the original.