Add operation scheduler

Problem

BBO operations need a scheduler/coordinator to manage the execution of batched operations efficiently. Currently there's no mechanism to:

1. Periodically find and queue active BBO migrations
2. Act as the entry point for the BBO system
3. Coordinate job execution across the system

Solution

Implement a SingleDatabaseWorker that acts as a cron job scheduler/coordinator, similar to the existing BBM pattern.

The worker should:

• Run periodically to find active BBO migrations for a specific database

• Queue individual migration jobs for execution

• Serve as the main entry point for the BBO system

• Add SingleDatabaseWorker scheduler/coordinator