Hackage search gives broken URLs

Reproduction steps:

1. Go to https://hackage.haskell.org/package/filepath-1.5.2.0
2. Press 's' to search for something, say `takeDirectory`.
3. Click on one of the results.
4. Get 404 because the URL is https://hackage.haskell.org/package/filepath-1.5.2.0/docs//package/template-haskell-2.19.0.0/docs/System-FilePath-Posix.html#v:takeDirectory

Reproduce the issue at the filepath-1.5.2.0 Hackage page by pressing “s”, searching for `takeDirectory`, and opening a result. Inspect how the result URL is assembled, especially the duplicated `/package/.../docs/` segment. Done means the result opens the intended documentation page instead of returning 404.

Written by the indexing model from the issue text.