inline common-darwin into poppy (only one darwin host for now)

- merged common-darwin/default.nix content into hosts/poppy/default.nix
- removed hosts/common-darwin/
- removed ./hosts/common-darwin import from mkDarwin in flake.nix

linux hosts/common/ stays — already 2 linux hosts (muscari + rosemary)

hosts/common-darwin/default.nix

@@ -1,20 +0,0 @@
-{ pkgs, ... }:
-{
-  # flake + nix-command
-  nix.settings.experimental-features = [
-    "nix-command"
-    "flakes"
-  ];
-
-  # nix daemon (multi-user install)
-  services.nix-daemon.enable = true;
-
-  users.users.mikl = {
-    home = "/Users/mikl";
-    shell = pkgs.zsh;
-  };
-
-  environment.systemPackages = [
-    pkgs.vim
-  ];
-}

hosts/poppy/default.nix

@@ -1,4 +1,4 @@
-{ ... }:
+{ pkgs, ... }:
 {
   networking.hostName = "poppy";
 
@@ -6,4 +6,22 @@
   nixpkgs.config.allowUnfree = true;
 
   system.primaryUser = "mikl";
+
+  # nix settings
+  nix.settings.experimental-features = [
+    "nix-command"
+    "flakes"
+  ];
+
+  # nix daemon (multi-user install)
+  services.nix-daemon.enable = true;
+
+  users.users.mikl = {
+    home = "/Users/mikl";
+    shell = pkgs.zsh;
+  };
+
+  environment.systemPackages = [
+    pkgs.vim
+  ];
 }