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>

backend/cmd/api/main.go

@@ -8,6 +8,8 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strings"
+	"sync"
 	"syscall"
 	"time"
 
@@ -78,6 +80,9 @@ func main() {
 		Logger: logger,
 	})
 
+	// Create FAA TFR client
+	faaClient := client.NewFAAClient()
+
 	// Create HTTP server
 	srv := server.New(cfg.Addr(), logger)
 
@@ -88,6 +93,7 @@ func main() {
 		config:        cfg,
 		weatherSvc:    weatherSvc,
 		assessmentSvc: assessmentSvc,
+		faaClient:     faaClient,
 	}
 	srv.SetupRoutes(handler)
 
@@ -194,6 +200,12 @@ type Handler struct {
 	config        *config.Config
 	weatherSvc    *service.WeatherService
 	assessmentSvc *service.AssessmentService
+	faaClient     *client.FAAClient
+
+	// TFR cache
+	tfrCache   []model.TFR
+	tfrCacheAt time.Time
+	tfrCacheMu sync.RWMutex
 }
 
 // Health handles health check requests
@@ -371,6 +383,63 @@ func (h *Handler) AssessConditions(w http.ResponseWriter, r *http.Request) {
 	server.RespondJSON(w, 200, response)
 }
 
+const tfrCacheTTL = 30 * time.Minute
+
+// GetTFRs handles airspace TFR requests
+func (h *Handler) GetTFRs(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+
+	// Check cache
+	h.tfrCacheMu.RLock()
+	if h.tfrCache != nil && time.Since(h.tfrCacheAt) < tfrCacheTTL {
+		tfrs := h.tfrCache
+		h.tfrCacheMu.RUnlock()
+		server.RespondJSON(w, 200, map[string]interface{}{
+			"tfrs":         tfrs,
+			"count":        len(tfrs),
+			"last_checked": h.tfrCacheAt.UTC(),
+		})
+		return
+	}
+	h.tfrCacheMu.RUnlock()
+
+	// Fetch from FAA
+	allTfrs, err := h.faaClient.FetchTFRs(ctx)
+	if err != nil {
+		h.logger.Error("failed to fetch TFRs", "error", err)
+		// Return empty on error — don't show banner
+		server.RespondJSON(w, 200, map[string]interface{}{
+			"tfrs":         []model.TFR{},
+			"count":        0,
+			"last_checked": time.Now().UTC(),
+		})
+		return
+	}
+
+	// Filter by configured state
+	var filtered []model.TFR
+	for _, tfr := range allTfrs {
+		if strings.EqualFold(tfr.State, h.config.LocationState) {
+			filtered = append(filtered, tfr)
+		}
+	}
+	if filtered == nil {
+		filtered = []model.TFR{}
+	}
+
+	// Update cache
+	h.tfrCacheMu.Lock()
+	h.tfrCache = filtered
+	h.tfrCacheAt = time.Now()
+	h.tfrCacheMu.Unlock()
+
+	server.RespondJSON(w, 200, map[string]interface{}{
+		"tfrs":         filtered,
+		"count":        len(filtered),
+		"last_checked": time.Now().UTC(),
+	})
+}
+
 // WeatherFetcher runs background weather fetching
 type WeatherFetcher struct {
 	logger     *slog.Logger