refactor(signal): use native signal-cli service

systems/jeeves/networking/firewall.nix

@@ -13,7 +13,6 @@ let
     open_webui = 8080;
     postgresql = 5432;
     share = 8091;
-    signal_cli = 8989;
     syncthing = 8384;
   };
 in
@@ -40,7 +39,6 @@ in
       ports.ollama
       ports.open_webui
       ports.postgresql
-      ports.signal_cli
       ports.syncthing
     ];
   };