goyplex: netbird from a fresher nixpkgs pin (0.81.x) to match the 0.81 server

flake.nix

@@ -2,6 +2,8 @@
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
 
+    nixpkgs-netbird.url = "github:nixos/nixpkgs/nixos-unstable";
+
     hyprland.url = "github:hyprwm/Hyprland";
     agenix.url = "github:ryantm/agenix";