Scaffold nikita-nixos host

Add a second nixosConfigurations entry for a friend's machine running
Plasma 6 + SDDM. The hardware-configuration.nix is a placeholder; it
must be replaced with the output of nixos-generate-config on the
actual hardware before installing. Git identity in hosts/nikita-nixos/
home.nix is also a placeholder.

hosts/nikita-nixos/home.nix

@@ -0,0 +1,24 @@
+{ ... }:
+
+{
+  imports = [
+    ../../home/zsh.nix
+    ../../home/fonts.nix
+    ../../home/yazi.nix
+    ../../home/symlinks.nix
+    ../../home/packages-base.nix
+  ];
+
+  home.username = "nikita";
+  home.homeDirectory = "/home/nikita";
+  home.stateVersion = "26.05";
+
+  # TODO: replace with Nikita's actual git identity before first use
+  programs.git = {
+    enable = true;
+    settings.user = {
+      name = "Nikita";
+      email = "nikita@example.com";
+    };
+  };
+}