[jrasell]

The region picker should display the configured region when the cluster is not federated. Previously the picker would return null if a region was not stored in localstorage which in single region clusters resulted in an empty region identifier.

The change ensures this is populated with the region identifier if no region is found in localstorage and there are no federated clusters.

Testing & Reproduction steps

Run nomad agent -dev -region=nmd-eng with and without this change and check the header on the UI landing page when authenticated.

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  changelog entry using the make cl command.
• Testing Please add tests to cover any new functionality or to demonstrate bug fixes and
  ensure regressions will be caught.
• Documentation If the change impacts user-facing functionality such as the CLI, API, UI,
  and job configuration, please update the Nomad product documentation, which is stored in the
  web-unified-docs repo. Refer to the web-unified-docs contributor guide for docs guidelines.
  Please also consider whether the change requires notes within the upgrade
  guide. If you would like help with the docs, tag the nomad-docs team in this PR.
• LLM Usage If an LLM was used to generate any code, please ensure and confirm you have read
  and followed the AI usage guide.

Reviewer Checklist

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  within the public repository.

[navyadas-dev]

LGTM 👍