make home-manager optional

As the home-manager depends on the actual used nixpkgs version
and is not always used, remove it from the base dependencies but
use still use it implictely if a home-manager input exists.

export/nixosConfigurations.nix

@@ -5,9 +5,13 @@
       modules = builtins.concatLists (map (base: builtins.attrValues (flake.lib.scan { base = "${base}/host/${name}"; })) flake.lib.schema.base)
         ++ [ { config.networking.hostName = name; } ]
         ++ [ nixosModules.default ]
-        ++ [ inputs.home-manager.nixosModules.default ]
-        ++ [ { config.home-manager.sharedModules = [ hmModules.default ]; } ]
-        ++ [ { config.home-manager.extraSpecialArgs = { inherit flake namespace; }; } ]
+        ++ inputs.${nixpkgs}.lib.optional (inputs ? home-manager) {
+          imports = [ inputs.home-manager.nixosModules.default ];
+          config.home-manager = {
+            sharedModules = [ hmModules.default ];
+            extraSpecialArgs = { inherit flake namespace; };
+          };
+        }
         ++ builtins.attrValues nixosUsers
         ++ builtins.attrValues nixosGroups
         ;

flake.lock

@@ -15,27 +15,6 @@
         "type": "github"
       }
     },
-    "home-manager": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1747688870,
-        "narHash": "sha256-ypL9WAZfmJr5V70jEVzqGjjQzF0uCkz+AFQF7n9NmNc=",
-        "owner": "nix-community",
-        "repo": "home-manager",
-        "rev": "d5f1f641b289553927b3801580598d200a501863",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "ref": "release-24.11",
-        "repo": "home-manager",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1751274312,
@@ -55,7 +34,6 @@
     "root": {
       "inputs": {
         "hardware": "hardware",
-        "home-manager": "home-manager",
         "nixpkgs": "nixpkgs"
       }
     }

flake.nix

@@ -2,10 +2,6 @@
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-24.11";
     hardware.url = "github:nixos/nixos-hardware";
-    home-manager = {
-      url = "github:nix-community/home-manager/release-24.11";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
   };
 
   outputs = { self, ... }@inputs: import ./lib/flake.nix inputs ./.;