Is your improvement request related to a feature? Please describe (👍 if you like this request)

In the current Longhorn V2 engine implementation, the function rounds the requested volume size to match the SPDK clusterSize (typically 1 MiB) and returns an error if the size is not aligned.

However, this logic introduces redundant and potentially inconsistent behavior because the longhorn-manager webhook (mutator.go) already rounds up the requested volume size to 2 MiB before persisting it.

Describe the solution you'd like

We should remove the volume spec size validation and rounding logic from the V2 engine's function (ex Expand() )in longhorn-spdk-engine, and instead move this validation entirely into the webhook layer in longhorn-manager.

Describe alternatives you've considered

No response

Additional context

No response