feat: manage UFM credentials per named InfiniBand fabric

[poroh]

Is this a new feature, an enhancement, or a change to existing functionality?

Enhancement

How would you describe the priority of this feature request

Medium

Please provide a clear description of problem this feature solves

CredentialKey::UfmAuth is fabric-aware internally, but credential handlers and admin CLI commands always target default.

Real and simulated UFM endpoints cannot be managed independently through supported interfaces.

Feature Description

UFM credential operations shall target an explicitly selected fabric.

Describe your ideal solution

Add optional fabric_id fields to UFM credential creation and deletion requests, defaulting to default.

Add --fabric-id to the relevant admin CLI commands for adding credentials, deleting credentials, and generating UFM certificates.

Describe any alternatives you have considered

No response

Additional context

No response

Code of Conduct

• I agree to follow NVIDIA Infra Controller's Code of Conduct
• I have searched the open feature requests and have found no duplicates for this feature request