make admins & timezones required

we talked about it and came to the conclusion that there's no point to have timezones & admins optional. there's tons of issues with no admins added, and also having no timezones results in strange behavior if someone requests with time. @kevinkreiser suggested we could host those somewhere so people can pull them without building. we could use github artifacts for that, triggered by a manual github action to re-create them. those artifacts are available for download via the github api. though they're only persisted for 90 days or so I think, but it's easy to automatically generate them every couple of months, github actions has cron capabilities.

could even auto-download them in the code eventually via a config url defaulting to the latest github artifact, but the whole HTTP/curl compilation logic seems a bit daunting currently..