Use uv and uv run pip for Dockerfile generation (#2747)
- Replace pyenv/pip with uv for Python installation (uv python install)
- Use UV_SYSTEM_PYTHON=true so uv operates on the system Python
- For user requirements (pip install -r), use 'uv run pip' which invokes
Python's own pip/OpenSSL stack, working around rustls's lack of P-521
ECDSA support needed for Cloudflare Warp MITM certificates
- Append CA cert directly to bundle file in addition to update-ca-certificates
for robustness across base images
- Update all tests to match new Dockerfile output
