gateway: converge, don't start/stop/reload

The gateway is a deployment (castle-gateway) — its lifecycle is the same
convergence as everything else, so the bespoke start/stop/reload verbs
(which still routed through the retired enable/disable path) are gone.

- CLI: `castle gateway` is now inspection only — bare or `status` shows
  the route table. Start/stop/reload it via `castle apply` (render routes
  + reload) or `castle restart castle-gateway`. Deletes the last users of
  `_service_enable`/`_service_disable`, so those are removed too.
- API: retire `POST /gateway/reload` (making routes live is `POST /apply`);
  `PUT /gateway/config` message + docstring now say apply, not deploy.
- UI: GatewayPanel's "Reload" button → "Apply" (useApply); drop the
  useGatewayReload hook; GatewaySettings points at `castle apply`.
- docs: `castle gateway reload|status` → `castle gateway` (status lens).

core 129 / cli 31 / api 59 pass; dashboard builds clean; live `castle
gateway` shows routes with no start/stop/reload; /gateway/reload removed
from the API.

app/src/components/GatewaySettings.tsx

@@ -4,7 +4,7 @@ import type { GatewayInfo } from "@/types"
 import { useSaveGatewayConfig } from "@/services/api/hooks"
 
 /** Editable gateway routing + public-exposure settings (domain / public_domain /
- *  tunnel / tls). Saves to castle.yaml; changes take effect on the next deploy. */
+ *  tunnel / tls). Saves to castle.yaml; changes take effect on the next apply. */
 export function GatewaySettings({ gateway }: { gateway: GatewayInfo }) {
   const { mutate: save, isPending, data: saved } = useSaveGatewayConfig()
   const [editing, setEditing] = useState(false)
@@ -44,7 +44,7 @@ export function GatewaySettings({ gateway }: { gateway: GatewayInfo }) {
           <button onClick={() => setEditing(false)} className="flex items-center gap-1 text-xs px-2.5 py-1 rounded bg-[var(--border)] text-[var(--muted)]">
             <X size={12} /> Cancel
           </button>
-          <span className="text-xs text-[var(--muted)]">Run <span className="font-mono">castle deploy</span> to apply.</span>
+          <span className="text-xs text-[var(--muted)]">Run <span className="font-mono">castle apply</span> (or the Apply button) to converge.</span>
         </div>
       </div>
     )