feat(portal): move edge proxy services from Jeeves

- move HAProxy and ACME certificate management to Portal
- route application backends to Jeeves over Tailscale
- restrict Jeeves backend ports to the Tailscale interface
- expose Gems for remote proxy access

systems/jeeves/services/nix_serve.nix

@@ -7,6 +7,6 @@ in
     package = pkgs.nix-serve-ng;
     enable = true;
     secretKeyFile = "${vars.secrets}/services/nix-cache/cache-priv-key.pem";
-    openFirewall = true;
+    openFirewall = false;
   };
 }