Restructure networking configuration to per-machine modules

- Move networking configs to modules/network/ directory
- Create network-<machine-name>.nix files for each machine
- Add common.nix for shared networking configuration
- Update import paths in machine configurations
- Reduce duplication by using common networking settings

Network modules:
- modules/network/common.nix: Shared settings (nftables, SSH, tailscale)
- modules/network/network-congenital-optimist.nix: Workstation specific
- modules/network/network-sleeper-service.nix: File server specific

modules/network/network-sleeper-service.nix

@@ -0,0 +1,21 @@
+# Networking Configuration - sleeper-service
+# Xeon file server network setup  
+{ config, pkgs, ... }:
+
+{
+  imports = [
+    ./common.nix
+  ];
+
+  # Machine-specific network configuration
+  networking = {
+    hostName = "sleeper-service";
+    networkmanager.enable = true;
+    
+    # Additional firewall ports for file server services
+    # (Add specific ports as needed for file sharing services)
+    firewall.allowedTCPPorts = [ 
+      # Add additional ports here as needed
+    ];
+  };
+}