Implement Logging and Observability Stack

Set up a comprehensive logging and observability system for this application:

**Structured Logging:**
- Logger factory with configurable transports (console, file, external service)
- Structured JSON format with consistent fields: timestamp, level, message, requestId, userId, duration
- Log levels: error, warn, info, debug, trace with environment-based filtering
- Request/response logging middleware with body redaction for sensitive fields
- Error logging with full stack traces and context

**Distributed Tracing:**
- Request correlation IDs propagated across services
- Span creation for key operations (DB queries, API calls, queue processing)
- Trace context injection in outgoing HTTP requests
- Performance timing for critical code paths

**Metrics:**
- Custom counters: request_count, error_count by endpoint
- Histograms: response_time, db_query_duration
- Gauges: active_connections, queue_depth
- Health check endpoint aggregating all service dependencies

**Alerting:**
- Error rate threshold alerts
- Latency degradation detection
- Health check failure notifications

Use existing libraries in the project or suggest minimal additions.