fix: address code review findings

cmd/api/handlers.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	"crypto/hmac"
+	"crypto/subtle"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -435,7 +435,7 @@ func adminAuth(hc *HandlerContext, w http.ResponseWriter, r *http.Request) bool
 		return false
 	}
 	providedAPIKey := r.Header.Get("X-Admin-Api-Key")
-	if !hmac.Equal([]byte(providedAPIKey), []byte(expectedAPIKey)) {
+	if subtle.ConstantTimeCompare([]byte(providedAPIKey), []byte(expectedAPIKey)) != 1 {
 		http.Error(w, "unauthorized", http.StatusUnauthorized)
 		return false
 	}

cmd/api/main.go

@@ -39,6 +39,35 @@ func main() {
 	http.HandleFunc("/internal/admin/stations/", makeHandler(AdminStationStatus, handlerCtx))
 	http.HandleFunc("/metrics", makeHandler(MetricsHandler, handlerCtx))
 
+	// User preferences routes
+	http.HandleFunc("/v1/preferences/saved-cities", func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			GetSavedCities(handlerCtx, w, r)
+		case http.MethodPost:
+			AddSavedCity(handlerCtx, w, r)
+		default:
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+	http.HandleFunc("/v1/preferences/saved-cities/", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == http.MethodDelete {
+			RemoveSavedCity(handlerCtx, w, r)
+		} else {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+	http.HandleFunc("/v1/preferences/search-history", func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			GetSearchHistory(handlerCtx, w, r)
+		case http.MethodPost:
+			AddSearchHistory(handlerCtx, w, r)
+		default:
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+
 	log.Println("Trip Planner API starting on :8080")
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }