feat(server): add request-scoped timeouts for runtime job dispatch

[martsokha]

Context

Long-running redaction jobs need deadline enforcement. No timeout propagation exists for runtime job dispatch.

Requirements

• Each job dispatched to the runtime carries a request-scoped deadline
• If the runtime does not return results within the deadline, the job is marked as timed out
• The caller is notified of the timeout (HTTP response or webhook event)
• Configurable default timeout per workspace or per job type
• Timeout is propagated through NATS JetStream message headers

References

• Server docs: ARCHITECTURE.md - Job Orchestration