feat(nixos): migrate system configuration

configs/nixos/registry/route.nix

@@ -0,0 +1,25 @@
+{ lib, ... }:
+{
+  checks = [
+    {
+      assertion = lib.registry.predicates.uniqueValue (entry: entry.value.domain);
+      message = "Route domains must be unique.";
+    }
+  ];
+
+  type = lib.types.submodule {
+    options = {
+      domain = lib.mkOption {
+        type = lib.types.str;
+        example = "files.alexion.dev";
+        description = "Public domain served by this reverse-proxy route entry.";
+      };
+
+      port = lib.mkOption {
+        type = lib.types.ints.between 1 65535;
+        example = 3923;
+        description = "Backend TCP port served by the matching address registry entry.";
+      };
+    };
+  };
+}