feat(3167): publish the swarm UI's name to agents and to local dev

Four wiring sites, same as forge/matrix/authelia: vhost, cert name, DNS,
local-dev hosts. This commit is the last two.

The apex is a SIBLING of forge./chat./auth., not a child of anything
dnsmasq already answers for, so the /<hive domain>/ rule does not cover
it - without an explicit record the name is unresolvable from every
agent netns while working fine from the host, which is the shape that
nearly shipped when authelia's name moved.

Published to agents deliberately (mara: publishing it is fine).
Reachability is not the access control: the vhost's auth_request plus
authelia's group:operators rule are, and an agent that resolves the name
still cannot open the page.

nix/host-modules/hive-gateway/default.nix

@@ -310,6 +310,7 @@ in
         forgeCfg
         matrixCfg
         autheliaCfg
+        uiCfg
         hyperhiveDomain
         ;
     };
@@ -334,6 +335,7 @@ in
         ) config.services.hyperhive.swarm.forge.domain
         ++ lib.optional (matrixCfg.enable && matrixCfg.gatewayHost != null) matrixCfg.gatewayHost
         ++ lib.optional autheliaCfg.enable autheliaCfg.domain
+        ++ lib.optional uiCfg.enable uiCfg.domain
       );
     };
   };