Intl.supportedValuesOf('timeZone') lists only canonical zones, so UTC,
Etc/UTC, GMT and Etc/GMT, which the server accepts, could not be chosen.
Merge them into the list, and keep the saved zone listed after another
is chosen so an alias such as US/Eastern can be chosen back.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>