refactor: move personal site to sites/nrd.sh/

Reorganize for monorepo structure:
- Move content/, templates/, static/, site.toml → sites/nrd.sh/
- Frees root for sukr docs site
- Build with: sukr -c sites/nrd.sh/site.toml

sites/nrd.sh/content/projects/nixpkgs.md

@@ -0,0 +1,6 @@
+---
+title: nixpkgs
+description: "ex-maintainer & NixOS release manager."
+weight: 2
+link_to: "https://github.com/NixOS/nixpkgs"
+---