settlement-engine worker uses a single process/thread without supervision

[therealjhay]

ProblemThe settlement worker is a single process; an unhandled rejection or crash takes all settlement jobs down until restarted manually.

1. No supervisor/restart.
2. Unhandled rejections not caught at top level.
3. Jobs stuck while process is down.

Solution

• Add top-level error handling and process supervision (or run under PM2/systemd).
• Ensure BullMQ jobs are retried after restart.
• Test crash-recovery.

Acceptance Criteria

• Process restarts automatically after crash.
• Jobs resume.
• pnpm --filter settlement-engine build passes.

Note for Contributors: Write a clear PR description. Show a crash-restart-recovery test.

[coderolisa]

Hello Maintainer,

I'd like to work on this issue. I've reviewed the requirements and can complete the implementation as specified.

Please assign it to me. Thank you!