infra: add flake module and crocus exports

infra/flake-module.nix

@@ -0,0 +1,18 @@
+{
+  flake.infra =
+    let
+      tf_outputs = builtins.fromJSON (builtins.readFile ../infra/outputs.json);
+    in
+    {
+      machines = {
+        verbena = {
+          ipv4 = tf_outputs.verbena_ipv4.value;
+          ipv6 = tf_outputs.verbena_ipv6.value;
+          gateway6 = tf_outputs.verbena_gateway6.value;
+        };
+        crocus = {
+          ipv4 = tf_outputs.crocus_ipv4.value;
+        };
+      };
+    };
+}