Fix major scheduling bug where only active tasks were checked for conflicts.
Changes:
- Check PENDING tasks: Prevent scheduling if task is queued for same volume
- Check ASSIGNED/ACTIVE tasks: Prevent scheduling if task is running on same volume
- Check RECENT tasks: Prevent immediate re-scheduling on same volume after completion
This prevents dangerous scenarios like:
❌ Scheduling vacuum while another vacuum is pending on same volume
❌ Scheduling balance while erasure coding is queued for same volume
❌ Immediately re-scheduling failed tasks without cooldown period
Critical safety improvement ensuring comprehensive volume-level task isolation.
chrislu
72f0a47563