Feature: Implement queue worker for processing jobs

[3m1n3nc3]

Description:
H3ravel needs a worker system to process queued jobs independently of the HTTP lifecycle.

This issue focuses on job execution, not dispatching.

Goals:

• Worker process that pulls jobs from the queue
• Executes job handle() method
• Handles retries and failures
• Graceful shutdown support

Acceptance Criteria:

• Jobs are processed via worker
• Failures trigger retry logic
• Worker can run as a standalone process