Add Messenger Support to Automators

Problem/Motivation

Implement background processing support for Automators using the new AI Messenger system, enabling long-running automations to be processed asynchronously.

Currently, automators run directly, in batch or via cron which:

• Direct run can timeout during long operations and doesn't handle interruptions
• Batch doesn't handle interruptions and isn't triggered on Entity save
• Cron tasks can timeout during long operations and can get stuck
• None of the above can be distributed across workers

Proposed resolution

1. Background Processing
   • Integration with ai_messenger
2. New Execution Mode
   • Background (new, messenger-based)
3. Configuration
   • Retry policies
   • Default value
   • Graceful error responses

User interface changes

• New execution mode

API changes

• Progress callbacks