feat(hm): add sharedModules, move configurations.nix to hosts.nix

nix/modules/hosts.nix

@@ -0,0 +1,34 @@
+{
+  config,
+  lib,
+  inputs,
+  ...
+}:
+let
+  inherit (lib) nixosSystem;
+  inherit (cfg.lib) flattenAttrs;
+  inherit (lib.attrsets) mapAttrs;
+  cfg = config.flake;
+  hosts = cfg.manifest.hosts or { };
+  mkConfigurations =
+    class: hosts:
+    mapAttrs (
+      name: value:
+      if class == "nixos" then
+        nixosSystem {
+          specialArgs = {
+            inherit inputs;
+            hostName = name;
+          };
+          modules = [
+            (flattenAttrs cfg.modules.nixos)
+            (value.extraCfg or { })
+          ];
+        }
+      else
+        { }
+    ) hosts;
+in
+{
+  flake.nixosConfigurations = mkConfigurations "nixos" hosts.nixos;
+}