Allow `uv sync --no-install-project` without relying on `pyproject.toml`

[albertferras-vrf]

I'm trying the new feature in today's 0.3.3 release: uv sync --no-install-project but I could not make it work since it keeps failing because pyproject.toml file is not found

The full Dockerfile example provided in the documentation here https://docs.astral.sh/uv/guides/integration/docker/#intermediate-layers does not work and raises this error too