ansible: run the another-im/interop runner on asxpio-services

The interop project kept a cx23 (claude-test-interop-runner, about
EUR 6/month with its IPv4) only to run its Forgejo runner. Run it here
instead, with the same registration (UUID + token, token in the vault)
and the same three labels, pinned.

Its PR checks are untrusted, so unlike our own runner its jobs get
neither the Docker socket nor host volumes. nix-host, which on the old
host used the host's Nix store as a cache, is a throwaway container for
now; a second, trusted-only registration can bring the cache back.

Rollback: remove the role from site.yaml (or stop the container) and
start the old runner VM again.

Assisted-by: Claude:opus-5-5

ansible/site.yaml

@@ -43,6 +43,12 @@
   roles:
     - { role: restic_backup, tags: [restic] }
 
+- name: another-im/interop runner
+  hosts: services_servers
+  become: true
+  roles:
+    - { role: forgejo_runner_interop, tags: [forgejo_runner_interop] }
+
 - name: Bucket replica
   hosts: services_servers
   become: true