refactor: split tailscale into own module

modules/networking.nix

···
       # dnsovertls = "trues";
     };
 
-    services.tailscale = {
-      enable = true;
-      openFirewall = true;
-      useRoutingFeatures = "client";
-    };
-
     # services.mullvad-vpn.enable = true;
     # services.mullvad-vpn.package = pkgs.mullvad-vpn;
 

modules/tailscale.nix

···
+{delib, ...}:
+delib.module {
+  name = "tailscale";
+
+  options = delib.singleEnableOption true;
+
+  nixos.ifEnabled.services.tailscale = {
+    enable = true;
+    openFirewall = true;
+    useRoutingFeatures = "client";
+  };
+
+  # home.ifEnabled.services.tailscale-systray.enable = true;
+}