Observability: Structured Logging + Tracing (OpenTelemetry) #10
Description
Summary
Add structured logs and optional OpenTelemetry tracing across services and inter-node calls.
Scope
- Replace ad-hoc logs with structured fields (file_id, chunk_id, raft_term, peer).
- Context propagation across gRPC.
- Exporters: stdout/OTLP selectable.
Acceptance Criteria
- Spans visible for store/read flows across nodes.
- Log fields consistent across services.
- Toggle via config and env vars.
Notes
Provide sample traces and Kibana/Grafana screenshots in docs.