The Messages UI trusted only the per-device IndexedDB key, so if the server's
key record was gone (deleted, DB-restored, admin-reset) while a stale private
key lingered in the browser, the app looked 'unlocked' but no one could be
messaged and no setup was offered. Add useKeyState (server 'configured' AND
local unlock): show setup when the server has no key (setup overwrites the stale
local key), unlock when it has one this device hasn't opened, ready otherwise.
ChatThread is now self-contained. Also fix the header title on the Messages and
Notifications pages (was falling through to 'Channel manager').
963afa33a6