feat(admin): power controls — stop everything & power off, restart everything

Settings gains a second service button next to restart: stop every managed
local model server and exit the gateway process (nothing is respawned; in
Docker the restart policy decides). The SPA replaces itself with a static
"gateway is off" screen since the API is gone. The restart button is
relabeled "Restart everything" to say what it always did — the gateway
re-execs itself and managed servers come back with it. Translated in all
seven languages.

src/admin/mod.rs

@@ -184,6 +184,7 @@ pub fn api_routes(admin_token: String) -> Router<SharedState> {
         .route("/admin/api/logs", get(get_logs).delete(clear_logs))
         .route("/admin/api/system", get(get_system))
         .route("/admin/api/restart", post(restart_gateway))
+        .route("/admin/api/shutdown", post(shutdown_gateway))
         .route("/admin/api/bench", get(bench_list).post(bench_start))
         .route("/admin/api/config/export", get(config_export))
         .route("/admin/api/config/import", post(config_import))
@@ -2272,6 +2273,20 @@ async fn get_system(State(state): State<SharedState>) -> ApiResult {
     ok(serde_json::to_value(snap).unwrap_or_else(|_| json!({})))
 }
 
+/// Stop every managed local model server and power the gateway off. The 200
+/// goes out first so the SPA can show its "gateway is off" screen; nothing is
+/// respawned — the operator starts the gateway again by hand (or the Docker
+/// restart policy does, in which case this behaves like a restart).
+async fn shutdown_gateway(State(state): State<SharedState>) -> ApiResult {
+    state.cmf.stop().await;
+    tokio::spawn(async move {
+        tokio::time::sleep(std::time::Duration::from_millis(300)).await;
+        tracing::info!("shutdown requested from the admin console");
+        std::process::exit(0);
+    });
+    ok(json!({ "ok": true }))
+}
+
 /// Restart the gateway in place: stop managed model servers, spawn a fresh
 /// copy of ourselves (it retries the bind while our port frees), then exit.
 /// In Docker we only exit — we are PID 1, a spawned child would die with the