Match the settings popup to the browser/OS dark mode preference

popup.js

@@ -55,9 +55,10 @@ document.addEventListener("DOMContentLoaded", () => {
 
   function showStatus(message, isError) {
     status.textContent = message;
-    status.style.color = isError ? "#c0392b" : "#2a8f2a";
+    status.classList.toggle("error", !!isError);
     setTimeout(() => {
       status.textContent = "";
+      status.classList.remove("error");
     }, 1500);
   }