refactor: extract host config into 'host.nix' files

hosts/eetion/default.nix

@@ -8,14 +8,10 @@
     ./hard.nix
     ../../modules/ssh
     ../../modules/common
+    ./host.nix
     # ../../modules/uptime-kuma
   ];
 
-  host = {
-    username = "h";
-    name = "eetion";
-  };
-
   ssh = {
     inherit (config.host) username;
     publicHostname = config.host.name;

hosts/eetion/host.nix

@@ -0,0 +1,4 @@
+{
+  username = "h";
+  name = "eetion";
+}