Add flake.nix for Reticulum-Go development environment setup

flake.nix

@@ -0,0 +1,46 @@
+{
+  description = "Reticulum-Go development environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+
+        go = pkgs.go_1_24;
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            go
+            go-task
+            revive
+            gnumake
+          ];
+
+          shellHook = ''
+            echo "Reticulum-Go development environment"
+            echo "Go version: $(go version)"
+            echo "Task version: $(task --version 2>/dev/null || echo 'not available')"
+            echo "Revive version: $(revive --version 2>/dev/null || echo 'not available')"
+          '';
+        };
+
+        packages.default = pkgs.buildGoModule {
+          pname = "reticulum-go";
+          version = "dev";
+          src = ./.;
+          vendorHash = "";
+          subPackages = [ "cmd/reticulum-go" ];
+          ldflags = [ "-s" "-w" ];
+          CGO_ENABLED = "0";
+        };
+      });
+}
+