fix: using json response header

backend/main.go

@@ -116,7 +116,15 @@ func main() {
 	}()
 
 	r := chi.NewRouter()
+
 	r.Use(middleware.Logger)
+	r.Use(func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Add("Content-Type", "application/json")
+
+			next.ServeHTTP(w, r)
+		})
+	})
 
 	r.Options("/*", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Add("Access-Control-Allow-Origin", "*")