Serve kredits-github via openresty, on Node 22

Move kredits-github onto Node 22.23.4 and behind the openresty reverse proxy
on the proxy hosts, replacing its own nginx + the custom haproxy entry.

- pin Node 22.23.4; run the app with HOST=0.0.0.0 / NODE_ENV=production and
  open port 3000 to 10.1.1.0/24 so the proxy can reach it over ZeroTier
- create /opt/kredits-github owned by the deploy user before cloning
- add kredits-github::nginx_proxy (tls_cert_for + openresty_site, upstream
  from role:kredits_github) and register it in the openresty_proxy run list
- drop the app-node nginx recipe/template and its role entry

roles/openresty_proxy.rb

@@ -38,6 +38,7 @@ production_run_list = %w(
   kosmos-hubot::nginx_botka_irc-libera-chat
   kosmos-hubot::nginx_hal8000_xmpp
   kosmos-ipfs::nginx_public_gateway
+  kredits-github::nginx_proxy
   kosmos-mastodon::nginx
   remotestorage_discourse::nginx
   sockethub::nginx