Fix: Clear pending scheduled items on thread reset

Recurring schedules created by a nightly scenario were incorrectly surviving thread resets. This caused them to fire notifications in subsequent, unrelated scenarios.

• Fixes an issue where recurring schedules persist across thread resets.

• Adds a step to delete ‘pending’ scheduled_items during DB transactions.

• Specifically targets scheduled items matching the current channel.

• Response now includes a count of cleared scheduled_items.