fix: address code review findings

- Fix type mismatch in search_cache.go: SearchWithCache now returns *yandex.Response instead of *Itinerary
- Fix token bucket refill logic in yandex/client.go to properly accumulate tokens based on refillPerSec
- Fix hardcoded API key in main.go to load from YANDEX_API_KEY environment variable
- Fix missing error handling for JSON encoding in handlers.go RouteGeoJSON function
- Fix incorrect redis.Nil handling in cache/store.go CacheAside.Exists method
- Fix incorrect error return type in station_status.go updateStationStatus to return newStatus instead of empty string

cmd/api/main.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"log"
 	"net/http"
+	"os"
 
 	"github.com/go-redis/redis/v8"
 
@@ -17,7 +18,12 @@ func main() {
 	redisClient := initRedis()
 	router := routing.NewGraph()
 	m := metrics.New()
-	yandexClient := yandex.NewClient("default-key", yandex.WithMetrics(m))
+
+	apiKey := os.Getenv("YANDEX_API_KEY")
+	if apiKey == "" {
+		apiKey = "default-key" // fallback for development
+	}
+	yandexClient := yandex.NewClient(apiKey, yandex.WithMetrics(m))
 
 	handlerCtx := NewHandlerContext(redisClient, router, yandexClient, m)
 
@@ -62,4 +68,4 @@ func makeHandler(handler func(*HandlerContext, http.ResponseWriter, *http.Reques
 	return func(w http.ResponseWriter, r *http.Request) {
 		handler(hc, w, r)
 	}
-}
+}