chore(nix): add Headscale service to MX configuration

- Included `headscale.nix` in the MX system configuration for VPN management.
- Added Nginx and ACME configuration to route traffic securely to Headscale.
- Ensures Headscale is enabled with required settings and packaged in the system.

systems/x86_64-linux/mx/default.nix

@@ -7,6 +7,7 @@
     ./coturn.nix
     ./forgejo.nix
     ./hardware-configuration.nix
+    ./headscale.nix
     ./kicker.nix
     ./mailserver.nix
     ./network.nix

systems/x86_64-linux/mx/headscale.nix

@@ -0,0 +1,32 @@
+{ config }:
+let
+  domain = "headscale.hoyer.xyz";
+in
+{
+  services = {
+    headscale = {
+      enable = true;
+      address = "0.0.0.0";
+      port = 8080;
+      server_url = "https://${domain}";
+      dns = {
+        baseDomain = "hoyer.tail";
+      };
+      settings = {
+        logtail.enabled = false;
+      };
+    };
+
+    nginx.virtualHosts.${domain} = {
+      useACMEHost = "hoyer.xyz";
+      forceSSL = true;
+      enableACME = true;
+      locations."/" = {
+        proxyPass = "http://localhost:${toString config.services.headscale.port}";
+        proxyWebsockets = true;
+      };
+    };
+  };
+
+  environment.systemPackages = [ config.services.headscale.package ];
+}