Add a small Node script that starts `backend/run.py` in a robust cross-platform way. It should detect and try backend launch commands in order, so Windows users can still use one command (`npm run dev`) even if `uv` is not installed but `python`/`py` is available.
Affected files: dev-backend.js
Signed-off-by: ChinhLee <76194645+chinhkrb113@users.noreply.github.com>
ChinhLee