feat: rework to modular

modules/roles/backend.nix

@@ -0,0 +1,13 @@
+{ ... }:
+{
+  imports = [
+    ./minimal.nix
+    ../dev/node.nix
+    ../dev/go.nix
+    ../dev/docker.nix
+    ../services/ssh.nix
+    ../services/gpg.nix
+    ../secrets/openbao.nix
+    ../optional/devtools.nix
+  ];
+}