scheduler does not apply schedule updates until restart

[maxcountryman]

Summary

A running scheduler reads the queue schedule once and then iterates indefinitely. Schedule changes made in DB are not applied until restart/reconnect.

Evidence

• Schedule loaded once before loop: src/scheduler.rs:362
• Explicit TODO in code: src/scheduler.rs:379

Why this matters

Operational schedule changes should take effect predictably without requiring process restarts.

Proposed direction

• Add schedule-change notification/listener, or periodic refresh with version/checksum detection.
• Handle unschedule/reschedule transitions safely while running.

Acceptance criteria

• Updating a queue schedule in DB while scheduler is running is reflected within bounded time.
• Unschedule takes effect without process restart.