Add third Kentland NetRID flight

[vgrafe]

Summary

• add a third nominal flight to the Kentland NetRID KML fixture
• give the new flight unique operator and aircraft metadata
• keep the existing Kentland resource and suite wiring unchanged

Motivation

Fixes #1533. The slow-update scenario requires one nominal flight per SP under test, but the Kentland fixture only provided two flights. A 3-SP run therefore failed before reaching scenario checks.

I recognize this is not a long-term solution but need immediate unlock so here it is. I will open another PR with something more future-proof.

Validation

• Parsed the Kentland KML through FlightDataResource: 3 flights with telemetry counts [65, 67, 89]
• Checked injected_flights_errors for the first 3 generated test flights: 0 errors
• PYTHONPATH=../.. ../../.venv/bin/pytest resources/netrid/flight_data_resources_test.py