add test for port uniqueness

flake.nix

@@ -62,12 +62,10 @@
         music_dir = "/${zpool_ssds}/music";
         torrent_group = "media";
 
-        # TODO: add checks to make sure none of these collide
         ports = {
           https = 443;
           jellyfin = 8096; # no services.jellyfin option for this
           torrent = 6011;
-          ollama = 11434;
           bitmagnet = 3333;
           owntracks = 3825;
           gitea = 2283;
@@ -170,7 +168,27 @@
             ];
         };
         modules =
+          # SAFETY! make sure no ports collide
           [
+            (
+              { lib, ... }:
+              {
+                config = {
+                  assertions = [
+                    {
+                      assertion =
+                        let
+                          ports = lib.attrValues service_configs.ports;
+                          uniquePorts = lib.unique ports;
+                        in
+                        (lib.length ports) == (lib.length uniquePorts);
+                      message = "Duplicate ports detected in 'ports' configuration";
+                    }
+                  ];
+                };
+              }
+            )
+
             ./disk-config.nix
             disko.nixosModules.disko
             ./configuration.nix