Artifact individual file view should have a back reference to the owning artifact

When viewing an artifact component such as https://debusine.debian.net/debian/base/artifact/1367615/file/hdf5-blosc_1.0.1-1.debian.tar.xz, there is no clickable link back to the owning artifact https://debusine.debian.net/debian/base/artifact/1367615/. One can get back by deleting part of the URL, so the lack of such a link is a minor inconvenience.