Add live flight map inset

[ianrelecker]

Summary

• carry OpenSky live position data onto each enriched flight
• render a configurable local map inset for the currently rotated flight card
• cache the latest flights so display rotation continues between network fetches
• document the map toggle and marker color settings

Validation

• /Users/ian/Library/Python/3.9/bin/pio run -d firmware

Note: the build still emits existing ArduinoJson deprecation warnings in the fetcher code.