Update to (somewhat?) dendritic pattern

Heavily inspired by https://github.com/Doc-Steve/dendritic-design-with-flake-parts.

> Atomic commits? Never heard of them!

modules/hosts/keith/networking.nix

@@ -0,0 +1,31 @@
+{
+  flake.modules.nixos.keith = {
+    networking.hostName = "keith";
+
+    networking.networkmanager = {
+      enable = true;
+      ensureProfiles.profiles = {
+        p2p-nas = {
+          connection = {
+            id = "p2p-nas";
+            type = "ethernet";
+            interface-name = "enp1s0";
+            autoconnect = true;
+          };
+          ipv6 = {
+            method = "manual";
+            addresses = "fd00:fa57::1/64";
+          };
+          ipv4.method = "disabled";
+          ethernet.mtu = 9000;
+        };
+      };
+    };
+
+    networking.extraHosts = ''
+      fd00:fa57::2 duke.veltnet
+    '';
+
+    networking.firewall.enable = false;
+  };
+}