Turn the user directory into a sortable table

Turn the user directory into a sortable table

The list became a table with the same counts, and the column headers
order it: user, repositories, issues, changes, reviews, joining date.
Counts start largest-first and the name A to Z; clicking the active
header flips it. The active column carries aria-sort and an arrow.

The search, the status chips (everyone, active, no longer active), the
order and the page all live in the URL and are carried into every link,
so a view can be bookmarked and paging cannot change the question. It is
all server-side, so it works without JavaScript.

Sorting by a count needs every matched account's summary before the page
is cut, so the index now answers for the whole directory in one grouped
query — ActorSummaries — instead of a lookup for a page of names. That
also drops the per-request name list, so a large roster cannot run into
SQLite's bound-variable limit.

Retired accounts are marked in their row and can be filtered to rather
than living in a separate group, and a roster larger than one page is
covered by a test.