feat: create shared extraHosts module with Tailscale IPs

- Create modules/network/extraHosts.nix with Tailscale IP mappings
- Replace hardcoded networking.extraHosts in all machine configs
- Add extraHosts module import to all machines
- Enable Tailscale service by default in the module
- Use Tailscale mesh network IPs for reliable connectivity

modules/network/extraHosts.nix

@@ -0,0 +1,26 @@
+# Network hostname resolution module
+# Provides consistent hostname-to-IP mapping across all home lab machines
+# Uses Tailscale IPs for reliable connectivity across the mesh network
+
+{ config, lib, ... }:
+
+{
+  # Add hostname entries for all home lab machines using Tailscale IPs
+  networking.extraHosts = ''
+    # Home Lab Infrastructure (Tailscale mesh network)
+    100.109.28.53   congenital-optimist
+    100.81.15.84    sleeper-service  
+    100.119.86.92   grey-area
+    100.96.189.104  reverse-proxy vps1
+    
+    # Additional network devices
+    100.103.143.108 pihole
+    100.126.202.40  wordpresserver
+  '';
+  
+  # Enable Tailscale by default for all machines using this module
+  services.tailscale = {
+    enable = true;
+    useRoutingFeatures = "client";
+  };
+}