Preparation that loads Oban job data for delivery receipts.

Adds an oban_job field to each receipt containing:

• state: Job state (available, scheduled, executing, completed, etc.)
• queue: Queue name
• worker: Worker module
• scheduled_at: When the job is scheduled to run
• attempted_at: When the job was last attempted
• completed_at: When the job completed
• errors: Array of error maps
• attempt: Current attempt number
• max_attempts: Maximum number of attempts