nix: run swarm-ui wherever swarm-controller runs

Remove deploy.swarm-ui.enable. Every reader (the swarm-ui vhost, the
authelia operator rule for the swarm apex, hive-network's
anyServiceEnabled) now reads deploy.swarm-controller.enable, and the
controller's webhook public URL is gated on the swarm domain alone,
since the vhost it names exists wherever the daemon does.

Both spellings of the old switch (deploy.swarm-ui.enable and the
already-renamed swarm.ui.enable) become mkRemovedOptionModule entries,
so a host that still sets either fails evaluation with a message
naming the controller toggle instead of silently changing.

Ruling (mara, #3742): "swarm-ui always runs wherever controller runs".

Part of #3742

nix/host-modules/hive-network.nix

@@ -40,7 +40,6 @@ let
     lib.any lib.id [
       d.hive-controller.enable
       d.swarm-controller.enable
-      d.swarm-ui.enable
       d.forgejo.enable
       d.ci-runner.enable
       d.matrix.enable