Minor stack tweaks

[hazzuk]

Description

Small changes to the Jellyfin and Traefik stacks (based on recent user testing).

Changes

• Traefik now uses either a live or staging volume (based on karo_compose_traefik_acme_staging_enabled).
• Jellyfin no longer exposes its client discovery port.

Notes

• The Jellyfin client discovery port was always very unreliable during testing across different Jellyfin clients.
• Ahead of custom stacks, was important to remove any stack specific customisation inside the nftables config.

Checklist

• [n/a] Written documentation
• [n/a] Linked relevant issues