feat: enable ssh-agent and forwardAgent for homelab's machine

modules/system.nix

@@ -94,6 +94,11 @@
     openFirewall = true;
   };
 
+  # The OpenSSH agent remembers private keys for you
+  # so that you don’t have to type in passphrases every time you make an SSH connection. 
+  # Use `ssh-add` to add a key to the agent.
+  programs.ssh.startAgent = true;
+
   # Allow unfree packages
   nixpkgs.config.allowUnfree = true;