pinwheel: Extract age as module

hosts/pinwheel/modules/age/default.nix

@@ -0,0 +1,9 @@
+{ pkgs, ... }:
+{
+  age = {
+    identityPaths = [
+      "/etc/ssh/pinwheel"
+      "/home/alex/.ssh/alex.pinwheel"
+    ];
+  };
+}