- Add distributed tracing fields to Job struct (trace_id, correlation_id, parent_span_id, span_context)
- Create database migration 009_add_tracing for PostgreSQL and MySQL with optimized indexes
- Add job builder methods for tracing configuration (.with_trace_id(), .with_correlation_id(), etc.)
- Implement OpenTelemetry integration with OTLP export support (feature-gated)
- Add worker event hooks for job lifecycle monitoring (on_job_start, on_job_complete, etc.)
- Create comprehensive tracing.rs module with TraceId, CorrelationId, and TracingConfig types
- Add automatic span creation and trace context propagation for job processing
- Update documentation with tracing examples and feature flag information
- Maintain backward compatibility - existing jobs work unchanged
- Add 22 new tests for complete tracing functionality coverage

This enables production-ready distributed tracing for debugging and monitoring
job processing across service boundaries with integration to observability
platforms like Jaeger, Zipkin, and DataDog.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>