Keep when each account was added and when it last signed in

users.created comes back, beside a new last_login, for whoever maintains
the server. A password sign-in, the token link and a request through the
proxy all count, recorded to the hour so the proxy's per-request vouching
is not a write each time. Settings -> Users and ipx user list show both.
The three user queries now share one row mapping.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TAC7sLVqfKmY6rsTLXzNgk

CHANGELOG.md

@@ -10,11 +10,16 @@ The long form, with what was wrong before and how it was found, is in
 
 ## [Unreleased]
 
+### Added
+
+- Settings → Users and `ipx user list` show when each account was added and when it last signed
+  in, to the hour.
+
 ### Changed
 
 - Directory and Popular list the feeds inside an OPML one by one, and no longer the OPML itself,
   so you can subscribe to just the shows you want.
-- The database no longer records when accounts, subscriptions and sign-ins were created. Nothing
+- The database no longer records when subscriptions and sign-in sessions were created. Nothing
   ever read it, and an existing database drops the columns on its next start.
 
 ### Fixed