Apply Cache-Control overrides to response, not request headers (#14736)
## Summary
This was just an oversight on my part in the initial implementation.
Closes https://github.com/astral-sh/uv/issues/14719.
## Test Plan
With:
```toml
[project]
name = "foo"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.13.2"
dependencies = [
]
[[tool.uv.index]]
url = "https://download.pytorch.org/whl/cpu"
cache-control = { api = "max-age=600" }
```
Ran `cargo run lock -vvv` and verified that the PyTorch index response
was cached (whereas it typically returns `cache-control:
no-cache,no-store,must-revalidate`).
uv
d0efe1ed - Apply Cache-Control overrides to response, not request headers (#14736)
