Fix TriggerManager serialization causing WSOD

Problem

The TriggerManager service was causing a White Screen of Death (WSOD) when Drupal attempted to serialize it during certain operations. This prevented workflows from executing properly when triggers were involved.

Root Cause

The TriggerManager class contained non-serializable dependencies that were not properly handled during PHP serialization.

Solution

Applied proper serialization handling to the TriggerManager service to ensure it can be safely serialized and unserialized during Drupal's normal operations.

Impact

• Workflows with triggers now execute without causing fatal errors
• Improved stability of the trigger system