feat(nixos): migrate system configuration

configs/nixos/hosts/pikachu/hardware-configuration.nix

@@ -0,0 +1,18 @@
+{ lib, modulesPath, ... }:
+# Hardware detected from the Proxmox inventory for this machine.
+# disko derives the root disk filesystems, none declared here.
+{
+  imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
+
+  boot.initrd.availableKernelModules = [
+    "ahci"
+    "nvme"
+    "sd_mod"
+    "xhci_pci"
+  ];
+  boot.initrd.kernelModules = [ ];
+  boot.kernelModules = [ "kvm-intel" ];
+  boot.extraModulePackages = [ ];
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+}