v1.16.0

Users are now told whenever their second factors change, plus fixes to
notification preferences and push notifications.

Upgrading:

• No migrations, no configuration changes.
• Users start receiving account security notices for second-factor changes
  made after the upgrade. They cannot be turned off.
• Push notification titles are now localized, and some wording changed to
  match the in-app notification list (e.g. "forwarded your article" instead
  of "shared your article").

Added

• Account security notices. A user is notified when a security key is
  added to or removed from their account (with the key's label), and when
  TOTP two-factor authentication is set up or turned off.
  • The notices are sent from the functions that make the change, so no path
    can skip them.
  • They are always delivered, in-app and by push, whatever the notification
    preferences say.
  • Each notice links to /profile and says what to do if the user did not
    make the change.
  • This lets someone notice a change they did not make (see ADR 0022).

Fixed

• Some notification preferences could not be switched off. Turning off
  "liked your comment", "boosted your article" or "boosted your comment" on
  /profile failed with "Failed to update notification preferences." The page
  and the validation now share one list of notification types.
• Push notification icons never loaded. They pointed at an avatar path
  that does not exist; they now use the stored 120 px avatar.
• Push notification titles were English-only, and some types had no
  title. Comment likes and boosts showed "New notification". Titles now use
  the same translated text as the in-app notification list, in the
  recipient's preferred language.

Documentation

• The Ansible README explains rollback after an old Erlang/Elixir version
  is uninstalled. Re-deploying such a tag needs that version reinstalled.
  The immediate alternative is to repoint the current and static symlinks
  at a kept release and restart.