Add `/api/v2/test/grafana-table` endpoint to validate Grafana
table format compatibility before implementing the full time
range API.
- Create server/grafana.go with table format structures
- Add structured logging and OpenTelemetry tracing
- Include realistic NTP Pool sample data with null handling
- Set proper CORS and cache headers for testing
- Update implementation plan with Phase 0 completion status
Ready for Grafana JSON API data source integration testing.
