Scheduler Recurring Events

Show recurring series on SchedulerCalendar by expanding RFC 5545-style rules on master events.

• Standups, shifts, or maintenance windows that repeat daily or weekly
• Showing multiple synthetic instances inside the visible calendar window

• Set recurrence_rule on a master PlannedEvent using the supported subset (FREQ=DAILY, FREQ=WEEKLY with optional INTERVAL, BYDAY, COUNT, UNTIL).
• Enable SchedulerFeatures::RECURRING_EVENTS on SchedulerCalendar or SchedulerTimeline.

Expanded instances receive synthetic ids ({master_id}::{unix}) for display. Editing or dragging an instance updates the master event (series edit).