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'

frontend/components/weather/tfr-banner.tsx

@@ -0,0 +1,57 @@
+'use client'
+
+import { AlertTriangle, ExternalLink } from 'lucide-react'
+import { cn } from '@/lib/utils'
+import type { TFR } from '@/lib/types'
+
+interface TfrBannerProps {
+  tfrs: TFR[]
+  className?: string
+}
+
+export function TfrBanner({ tfrs, className }: TfrBannerProps) {
+  if (!tfrs || tfrs.length === 0) return null
+
+  return (
+    <div
+      className={cn(
+        'flex items-start gap-3 rounded-lg border border-red-500 bg-red-50 dark:bg-red-950 p-4',
+        className
+      )}
+      role="alert"
+    >
+      <AlertTriangle className="h-5 w-5 text-red-600 dark:text-red-400 flex-shrink-0 mt-0.5" />
+      <div className="flex-1">
+        <p className="text-sm font-medium text-red-800 dark:text-red-200">
+          {tfrs.length} Active TFR{tfrs.length !== 1 ? 's' : ''} in Area
+        </p>
+        <ul className="mt-1 space-y-1">
+          {tfrs.map((tfr) => (
+            <li key={tfr.notam_id} className="text-xs text-red-700 dark:text-red-300">
+              <span className="font-medium">{tfr.type}</span>
+              {tfr.description && <> &mdash; {tfr.description}</>}
+              {tfr.detail_url && (
+                <a
+                  href={tfr.detail_url}
+                  target="_blank"
+                  rel="noopener noreferrer"
+                  className="ml-1 inline-flex items-center gap-0.5 text-red-600 dark:text-red-400 hover:underline"
+                >
+                  Details <ExternalLink className="h-3 w-3" />
+                </a>
+              )}
+            </li>
+          ))}
+        </ul>
+        <a
+          href="https://tfr.faa.gov/tfr3/"
+          target="_blank"
+          rel="noopener noreferrer"
+          className="mt-2 inline-flex items-center gap-1 text-xs font-medium text-red-600 dark:text-red-400 hover:underline"
+        >
+          View all TFRs on FAA website <ExternalLink className="h-3 w-3" />
+        </a>
+      </div>
+    </div>
+  )
+}