`uv python list` does not respect `UV_PYTHON_INSTALL_MIRROR`

### Summary

When I run `uv python list --show-urls` with a set `UV_PYTHON_INSTALL_MIRROR`, it still lists the default `https://github.com/astral-sh/python-build-standalone/releases/download/...` URLs.

However, `uv python install` correctly downloads from the defined install mirror.

### Platform

Ubuntu 24.04, RHEL8; both x86_64

### Version

0.9.8

### Python version

Python 3.13.5