Track scheduled pipeline disable events with timestamp and reason

A customer (internal) experienced a critical incident where all their scheduled pipelines were automatically disabled during an Active Directory maintenance window.

LDAP synchronization ran and blocked all users, which cascaded into disabling all active scheduled pipelines.

The customer had to restore from backup and manually recover the list of previously active pipelines to restore their production environment.

Currently, there's no audit trail for when or why a scheduled pipeline was disabled. This makes it difficult to:

• Understand the root cause of pipeline disablement
• Recover from mass disablement events
• Audit compliance and operational changes
• Distinguish between intentional disablement and system-triggered disablement

Proposal

Add two new database columns to the scheduled pipelines table:

• disabled_at (timestamp): Records when the pipeline was disabled
• disabled_reason (string/enum): Captures why the pipeline was disabled (e.g., "user_action", "ldap_sync", "system_maintenance", "user_deactivation")