add c# back

modules/apps/dev.nix

@@ -19,6 +19,7 @@ in {
   config = mkIf cfg.enable {
     home-manager.users.${homeCfg.username} = {
       home.packages = with pkgs; [
+        dotnetCorePackages.sdk_9_0
         gcc
         ghex
         haskell.compiler.native-bignum.ghcHEAD
@@ -29,6 +30,7 @@ in {
         jetbrains.pycharm-professional
         jetbrains.rider
         jetbrains.webstorm
+        mono
         nodejs_22
         platformio-core
         python313