Docs: Windows install guide (WSL2 + Docker Desktop)

[matiasbaglieri]

Goal: a clear, copy-paste Windows path.

The CLI ships a nest-win32-x64.exe, but self-hosting on Windows (WSL2 + Docker Desktop) isn't documented end-to-end.

Scope

• docs/INSTALL-WINDOWS.md: enable WSL2, install Docker Desktop, clone, run ./setup.sh, open http://localhost
• Link it from README.md Resources and QUICKSTART.md

Great first issue — mostly writing + a couple of screenshots. Ask in Discord if you get stuck.