Schedules were entered and displayed as six field cron expressions. A
picker now offers a frequency, a weekday or day of the month and a time,
and turns that into the expression the backend stores; tables and the
dashboard show wording like "Every day at 03:00". An expression the
picker cannot express stays editable as cron.
This also fixes a broken preset: the backend's cron dialect counts Sunday
as 1 and rejects 0, so the "every Sunday" choice in the application
backup form produced an invalid expression. The picker emits weekday
names, and a test pins the dialect down.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>