cancel subscriptions on signup popup destroy

src/app/website/signup/RulesPopup.svelte

@@ -2,6 +2,7 @@
   import { rulesPopupState, rulesPopupRead } from './RulesPopup.ts';
   import { rules } from '../../../rules.ts';
   import { popupState } from '@components/popup/Popup.ts';
+  import { onDestroy } from 'svelte';
 
   const modalTimeoutSeconds = 30;
 
@@ -10,7 +11,7 @@
   let modalTimer = $state<ReturnType<typeof setInterval> | null>(null);
   let modalSecondsOpen = $state(import.meta.env.PROD ? 0 : modalTimeoutSeconds);
 
-  rulesPopupState.listen((value) => {
+  const cancel = rulesPopupState.subscribe((value) => {
     if (value == 'open') {
       modalElem.show();
       modalTimer = setInterval(() => modalSecondsOpen++, 1000);
@@ -18,10 +19,11 @@
       clearInterval(modalTimer!);
     }
   });
+
+  onDestroy(cancel);
 </script>
 
 <dialog
-  id="rules-popup"
   class="modal"
   onclose={() => {
     if ($rulesPopupState !== 'accepted') $rulesPopupState = 'closed';