feat: rework to modular

modules/services/tailscale.nix

@@ -0,0 +1,9 @@
+{ lib, pkgs, ... }:
+let
+  tailscale = lib.attrByPath [ "tailscale" ] null pkgs;
+in
+{
+  home.packages = builtins.filter (pkg: pkg != null) [
+    tailscale
+  ];
+}