SAM-56 Build athena image in balenaCloud builder

[JoshuaCWebDeveloper]

Metadata:

Original Estimate: 
Priority: Medium
Epic: SAM-5 Setup CI/CD, Deployment, and Automated testing

The balenaCloud builders are nearly twice as fast at building the athena image than QEMU.

Set up a flow where a device receives a built athena image and pushes it to GHCR. We’ll want to support concurrent releases, ideally by somehow blocking a release until the image for the current release is pushed.