add dotnet module

hosts/modules/langs/dotnet.nix

@@ -0,0 +1,61 @@
+{
+  lib,
+  pkgs,
+  pkgs-unstable,
+  ...
+}: let
+  dotnetVersions = [8 9 10];
+
+  dotnetCombined =
+    pkgs.dotnetCorePackages.combinePackages
+    (builtins.concatMap
+      (v: let
+        # dotnet = pkgs.dotnetCorePackages."dotnet_${builtins.toString x}";
+      in [
+        # dotnet.sdk
+
+        # the runtime+aspnetcore packaged with the sdk
+        pkgs.dotnetCorePackages."sdk_${builtins.toString v}_0"
+      ])
+      dotnetVersions);
+
+  # Custom packaged tools
+  dotnetTools = with lib; {
+    uno-check = with pkgs.dotnetCorePackages;
+      buildDotnetGlobalTool {
+        pname = "Uno.Check";
+        version = "1.32.17";
+
+        nugetHash = "sha256-BfTVF5uHu9/nyLXqdDEOHCxq6BVQWhsnDBbARzdLDAE=";
+
+        executables = "uno-check";
+
+        dotnet-sdk = dotnet_9.sdk;
+        dotnet-runtime = dotnet_9.runtime;
+
+        meta = {
+          homepage = "https://github.com/unoplatform/uno.check";
+          license = licenses.mit;
+          maintainers = [maintainers.emileclarkb];
+        };
+      };
+  };
+in {
+  environment.systemPackages = with pkgs; [
+    # .NET
+    dotnetCombined
+
+    # .NET Tools
+    dotnetTools.uno-check
+
+    # Mono
+    mono
+    # NOTE: nixpkgs-unstable uses .NET8 SDK
+    # WARNING: nixpkgs-25.05 uses .NET6 SDK (now marked insecure)
+    pkgs-unstable.msbuild
+
+    # .NET Framework Tools/Services
+    omnisharp-roslyn
+    netcoredbg
+  ];
+}