fix(zebra): replace Task.async with Wormhole to fix Cachex issue

[dexyk]

📝 Description

Replaced Task.async/await with the Wormhole library in Zebra.Workers.Scheduler.Org to resolve Cachex blocking issues.

When using Task.async/await inside Cachex.fetch/3, if the fallback function crashed or timed out, subsequent calls would block indefinitely, as described in the linked Cachex issue.

By switching to Wormhole.capture/4, the call is executed in a supervised process with timeout handling and proper cleanup, preventing Cachex lockups.

Added tests for error handling, timeouts, and caching behavior.

More details in this task.

✅ Checklist

• I have tested this change
• This change requires documentation update N/A