[relay] Add a release-wired UBI image variant (#7457)

* [relay] Add a release-wired UBI image variant

* [relay] Align the UBI image with the shared UBI pattern

Main now ships UBI variants of the client, combined server and proxy that
share one license collector and one image layout, and the Red Hat
certification workflow expects every certified image to carry both amd64
and arm64. The relay variant predated that, kept its own copy of the
license script, built amd64 only, and ran as UID 65532 on the privileged
default port :443, so it would not start under OpenShift or rootless Podman.

Use release_files/collect-licenses.sh and build amd64 and arm64 like the
other UBI images. Run as 1000:0 with a group-0 writable /var/lib/netbird
for Let's Encrypt data, and default the listener to :8443 so an arbitrary
non-root UID can bind it; the relay's Let's Encrypt flow uses TLS-ALPN on
that same listener, so no separate challenge port is needed.

* [infrastructure] Certify the relay UBI image on release

Releases certify the UBI images through redhat-certify.yml, which only
lists the client, proxy and combined server, so a released relay UBI
image would never reach the Red Hat catalog.

Add relay to the component list and the manual dispatch options. Its
Partner Connect ID comes from REDHAT_CERT_ID_RELAY, which must exist
before this merges: the resolve step fails the whole run when any
component's variable is missing.

.github/workflows/redhat-certify.yml

@@ -34,6 +34,7 @@ on:
           - reverse-proxy
           - netbird-server
           - signal
+          - relay
       version:
         description: "Released version, e.g. v0.80.0"
         type: string
@@ -70,6 +71,7 @@ jobs:
             "reverse-proxy ghcr.io/netbirdio/reverse-proxy -ubi"
             "netbird-server ghcr.io/netbirdio/netbird-server -ubi"
             "signal ghcr.io/netbirdio/signal -ubi"
+            "relay ghcr.io/netbirdio/relay -ubi"
           )
           matrix="[]"
           missing=()