deploy: separate "what this host deploys" from swarm-wide truth

`services.hyperhive.swarm.*` is meant to be identical on every host in a
swarm — it describes the swarm, and every hive needs all of it to be a
client. But it also carried the `enable` toggles, which are precisely the
values that must differ per machine. The namespace that should be the
same everywhere held the one thing that cannot be.

Adds `services.hyperhive.deploy.*` for a host's deployment decisions, and
moves the first of them (`swarm.grafana.enable` -> `deploy.grafana`) as
the pattern for the rest. Flat and named for the thing deployed rather
than grouped under a "swarm services" attribute: from the deploy side it
does not matter what kind of thing each one is, and a grouping by service
kind would re-encode the service-side taxonomy into a layer that does not
care about it.

Behaviour is unchanged. The move is a rename in the strict sense — same
type, same meaning, new path — so `mkRenamedOptionModule` carries it and
existing configs keep evaluating with one warning naming both paths. The
renames live in the new module rather than the service modules, so the
whole migration has a single home and a single file to delete when the
deprecation window closes.

nix/host-modules/default.nix

@@ -12,6 +12,7 @@
 {
   imports = [
     ./hyperhive.nix
+    ./deploy.nix
     ./local-defaults.nix
     ./hive-c0re
     ./hive-ci.nix