Turn absolute links into relative links.

Fixes #27925.

This reverts commit b0165cb03138e933a337ddc8400c3a8bbe889b3d.

Turns out that worst case query time goes up from 3 to 58 seconds with
the new query, which is unacceptable. We'll have to analyze and
improve the query on the production database before merging this
change.

We're now counting the hours for which we have statuses and exit
lists. More precisely, we're truncating consensus valid-after times
and exit scan times to the hour and counting how many distinct hours
we saw during the requested time. If we're missing 18 or more hours of
statuses or exit lists we're printing out a note in the summary.

Fixes #31071.

The default listen host is still 127.0.0.1, but now it's possible to
configure a different listen host, like 0.0.0.0, which can facilitate
local testing.

Implements part of #31649.