fix(postgres.nix): update configuration path to use services.postgresql

- Changed the configuration path from `postgresql` to `services.postgresql` for consistency and correctness.

hosts/architect/postgres.nix

@@ -1,7 +1,7 @@
 { pkgs, lib, ... }:
 
 {
-  postgresql = {
+  services.postgresql = {
     enable = true;
     package = lib.mkForce pkgs.postgresql;
   };