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/lib/types.ts

@@ -85,6 +85,24 @@ export interface AssessmentResponse {
   thresholds_used: Thresholds
 }
 
+// TFR (Temporary Flight Restriction) types
+
+export interface TFR {
+  date: string
+  notam_id: string
+  facility: string
+  state: string
+  type: string
+  description: string
+  detail_url: string
+}
+
+export interface TFRResponse {
+  tfrs: TFR[]
+  count: number
+  last_checked: string
+}
+
 // Error response type
 export interface APIError {
   error: string