OpenTelemetry tracing for query service

We instrumented the analytics query service with OpenTelemetry so request paths can be traced end-to-end.

1. OpenTelemetry SDK and exporter wiring added to the Data query service.
2. Each API request emits a span hierarchy covering authentication, query construction, query execution against the analytics store, and response serialization.
3. Slow-query investigations now have full trace context instead of needing manual log correlation.