Add TFR warning banner for airspace restrictions

Fetches active Temporary Flight Restrictions from the FAA website,
filters by configured state (LOCATION_STATE env var), and displays
a red warning banner at the top of the dashboard when TFRs are present.
Data is cached for 30 minutes and degrades gracefully if the FAA is unreachable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/components/weather/index.ts

@@ -4,3 +4,4 @@ export { WindDirectionChart } from './wind-direction-chart'
 export { ThresholdControls } from './threshold-controls'
 export { RefreshCountdown } from './refresh-countdown'
 export { StaleDataBanner } from './stale-data-banner'
+export { TfrBanner } from './tfr-banner'