Create dummy COOKIE file in Nix package to avoid runtime error

nix/package.nix

@@ -12,6 +12,9 @@ beamPackages.mixRelease rec {
   
   # Disable distributed Erlang to avoid COOKIE requirement
   postInstall = ''
+    # Create a dummy COOKIE file to satisfy the release boot script
+    echo "dummy_cookie" > $out/releases/COOKIE
+    
     # Create wrapper script that sets proper environment
     mv $out/bin/systant $out/bin/.systant-wrapped
     cat > $out/bin/systant << EOF

server/mix.exs

@@ -35,7 +35,6 @@ defmodule SystemStatsDaemon.MixProject do
         applications: [runtime_tools: :permanent],
         include_erts: true,
         strip_beams: false,
-        cookie: :disabled,
         env: %{
           "RELEASE_DISTRIBUTION" => "none",
           "RELEASE_NODE" => "nonode@nohost"