add gc

nixos/configuration.nix

@@ -10,7 +10,14 @@
   nix.settings.experimental-features = [
     "nix-command"
     "flakes"
+
   ];
+  nix.gc = {
+    automatic = true;
+    persistent = true;
+    dates = [ "daily" ];
+    options = "--delete-older-than 7d";
+  };
   nixpkgs.config.allowUnfree = true;
 
   # Secret Management