chore(nix): enable Tailscale on SGX, MX, and X1 systems

- Added `services.tailscale.enable = true` to the configurations of SGX, MX, and X1 systems for VPN support.
- Improves secure connectivity and simplifies network management across these systems.

systems/x86_64-linux/mx/default.nix

@@ -18,6 +18,8 @@
     ./users.nix
   ];
 
+  services.tailscale.enable = true;
+
   metacfg = {
     emailOnFailure.enable = true;
     base.enable = true;

systems/x86_64-linux/sgx/default.nix

@@ -11,6 +11,8 @@
     ./mail.nix
   ];
 
+  services.tailscale.enable = true;
+
   boot.tmp.useTmpfs = false;
 
   sops.secrets.pccs.sopsFile = ../../../.secrets/sgx/pccs.yaml;

systems/x86_64-linux/x1/default.nix

@@ -11,6 +11,8 @@ with lib.metacfg;
     ./hardware-configuration.nix
   ];
 
+  services.tailscale.enable = true;
+
   services.cratedocs-mcp.enable = true;
 
   sops.age.sshKeyPaths = [ "/var/lib/secrets/ssh_host_ed25519_key" ];