searx: Dark theme as default

hosts/architect/searx.nix

@@ -34,6 +34,7 @@ in
           infinite_scroll = true;
           query_in_title = true;
           results_on_new_tab = true;
+          theme_args.simple_style = "dark";
         };
 
         redis.url = "redis://127.0.0.1:${toString config.services.redis.servers."searx".port}";