Configure apt.itsallcode.org for the OpenFastTrace APT repository

[redcatbear]

Depends on #4.

After the signed APT repository is published, configure the custom domain apt.itsallcode.org for its hosting service. Point the required DNS records to the selected GitHub Pages endpoint, configure the custom domain in repository hosting settings, and enable HTTPS.

The resulting endpoint must serve the OpenFastTrace repository at https://apt.itsallcode.org/openfasttrace and preserve HTTPS for both the APT metadata and public key.

Acceptance criteria:

• apt.itsallcode.org resolves to the published repository hosting service.
• HTTPS is active with a valid certificate.
• https://apt.itsallcode.org/openfasttrace/dists/stable/InRelease is reachable.
• The custom-domain configuration remains compatible with automated repository publication.