Clean up networking configuration structure

- Remove leftover networking.nix files from machine directories
- ZFS configuration moved to machine-specific configuration where it belongs
- Network module now contains only networking-related configuration
- Improved separation of concerns between network and machine configs

machines/sleeper-service/networking.nix

@@ -1,34 +0,0 @@
-# Networking Configuration - sleeper-service
-# Xeon file server network setup  
-{ config, pkgs, ... }:
-
-{
-  # Network configuration
-  networking = {
-    hostName = "sleeper-service";
-    networkmanager.enable = true;
-    nftables.enable = true;
-    
-    # Firewall configuration for file server
-    firewall = {
-      enable = true;
-      allowedTCPPorts = [ 
-        22    # SSH
-        # Add other ports as needed for file sharing services
-      ];
-      allowedUDPPorts = [ ];
-    };
-  };
-
-  # VPN and remote access
-  services.tailscale.enable = true;
-  
-  # SSH configuration for headless server
-  services.openssh = {
-    enable = true;
-    settings = {
-      PermitRootLogin = "no";
-      PasswordAuthentication = false;
-    };
-  };
-}