Prompt for the scheduler timezone during interactive installs and support
a --time-zone flag for scripted installs.
Detect a sensible default from POBSYNC_TIME_ZONE, timedatectl, or
/etc/timezone before falling back to UTC, and validate the value with
Python zoneinfo before writing it to pobsync.env.
Document that schedules are evaluated in POBSYNC_TIME_ZONE so production
installs can avoid UTC/local-time ambiguity.
Peter van Arkel
39b6cf3469