add zammad to fw vm, add web-arm machine

hosts/web-arm/modules/postgresql.nix

@@ -0,0 +1,9 @@
+{ pkgs, ... }: {
+  services.postgresql.enable = true;
+  services.postgresql.package = pkgs.postgresql_14;
+  services.postgresql.settings = {
+    max_connections = "300";
+    shared_buffers = "80MB";
+  };
+  services.postgresqlBackup.enable = true;
+}