The pypi_download_file, pypi_simple_index, and pypi_package_versions endpoints
were using synchronous httpx.Client inside async functions. When upstream PyPI
servers respond slowly, this blocked the entire FastAPI event loop, preventing
health checks from responding. Kubernetes would then kill the pod after the
liveness probe timed out.
Changes:
- httpx.Client → httpx.AsyncClient
- client.get() → await client.get()
- response.iter_bytes() → response.aiter_bytes()
This ensures the event loop remains responsive during slow upstream downloads,
allowing health checks to succeed even when downloads take 20+ seconds.