feat: Complete sleeper-service systemd-networkd configuration

- Update sleeper-service to use systemd-networkd with static IP (10.0.0.8/24)
- Configure proper gateway (10.0.0.138) and DNS (Pi-hole, router, Google)
- Add NFS and SMB firewall ports for file server services
- Document network topology discovery results in plan.md
- Update network module README with current configuration status

Based on nmap network discovery and Context7 NixOS systemd-networkd documentation.
Configuration ready for deployment to existing files.home machine.

modules/network/network-sleeper-service.nix

@@ -1,5 +1,5 @@
 # Networking Configuration - sleeper-service
-# Xeon file server network setup  
+# Xeon file server network setup with systemd-networkd and static IPs
 { config, pkgs, ... }:
 
 {
@@ -10,12 +10,43 @@
   # Machine-specific network configuration
   networking = {
     hostName = "sleeper-service";
-    networkmanager.enable = true;
+    
+    # Enable systemd-networkd for static networking
+    useNetworkd = true;
+    useDHCP = false;  # Required when using systemd-networkd
+    
+    # Disable NetworkManager in favor of systemd-networkd
+    networkmanager.enable = false;
+    
+    # Configure static IP for the main ethernet interface
+    interfaces.enp0s25 = {
+      useDHCP = false;
+      ipv4.addresses = [
+        {
+          address = "10.0.0.8";  # Static IP for sleeper-service (existing files.home machine)
+          prefixLength = 24;
+        }
+      ];
+    };
+    
+    # Network gateway and DNS (based on nmap discovery)
+    defaultGateway = "10.0.0.138";  # Discovered router at lan.home
+    nameservers = [ "10.0.0.14" "10.0.0.138" "8.8.8.8" ];  # Pi-hole, router, Google DNS fallback
     
     # Additional firewall ports for file server services
-    # (Add specific ports as needed for file sharing services)
     firewall.allowedTCPPorts = [ 
+      111   # NFS portmapper
+      2049  # NFS
+      445   # SMB/CIFS
+      139   # NetBIOS Session Service
       # Add additional ports here as needed
     ];
+    
+    firewall.allowedUDPPorts = [
+      111   # NFS portmapper
+      2049  # NFS
+      137   # NetBIOS Name Service
+      138   # NetBIOS Datagram Service
+    ];
   };
 }