refactor: modularize golang development tools

Extract golang development tools from core user packages into optional module:

- Add go toolchain: go, gopls, goreleaser

Author: refnode

users/refnode/common/optional/golang.nix

@@ -0,0 +1,12 @@
+{ pkgs, ... }:
+
+{
+  # Go development tools
+  
+  home.packages = with pkgs; [
+    # Go toolchain
+    unstable.go
+    unstable.gopls
+    unstable.goreleaser
+  ];
+}

users/refnode/default.nix

@@ -6,6 +6,7 @@
     ./common/optional/rust.nix
     ./common/optional/mailtools.nix
     ./common/optional/backup.nix
+    ./common/optional/golang.nix
   ];
 
   # specify my home-manager configs
@@ -76,9 +77,6 @@
     unstable.graphviz
     unstable.plantuml-c4
     unstable.ffmpeg_7
-    unstable.go
-    unstable.gopls
-    unstable.goreleaser
     unstable.nodejs_22
     unstable.yubikey-manager
     unstable.platformio