Ensure 'add_device' API returns indexed-array (as per doco)

[claude191]

A prior commit removed the indexed-array around the returned value. This commit restores to prior behaviour so that existing integrations using the API do not have to change,

DO NOT DELETE THE UNDERLYING TEXT

Please note

Please read this information carefully. You can run ./lnms dev:check to check your code before submitting.

• Have you followed our code guidelines?
• If my Pull Request does some changes/fixes/enhancements in the WebUI, I have inserted a screenshot of it.
• If my Pull Request makes discovery/polling/yaml changes, I have added/updated test data.

Testers

If you would like to test this pull request then please run: ./scripts/github-apply <pr_id>, i.e ./scripts/github-apply 5926
After you are done testing, you can remove the changes with ./scripts/github-remove. If there are schema changes, you can ask on discord how to revert.

[laf]

LGTM, thanks @claude191

[librenms-bot]

This pull request has been mentioned on LibreNMS Community. There might be relevant details there:

https://community.librenms.org/t/22-4-0-changelog/18610/1