Scope overlays and modules to specific host sets

hosts/common.nix

@@ -1,6 +1,22 @@
-{ config, pkgs, ... }:
+{ config, pkgs, self, ... }:
 
 {
+  imports = [
+    self.inputs.agenix.nixosModules.age
+    self.inputs.home-manager.nixosModule
+    ../modules
+  ];
+
+  nixpkgs.overlays = [
+    self.inputs.agenix.overlays.default
+    (import ../overlays/default.nix)
+    (
+      final: prev: {
+        unstable = import self.inputs.nixpkgs-unstable { system = final.system; };
+      }
+    )
+  ];
+
   time.timeZone = "Europe/London";
 
   i18n.defaultLocale = "en_GB.UTF-8";