fix: harden extension security and plugin reliability

Address audit findings across background handlers, openers,
plugins, and UI: URL allowlists, XSS reductions, popup lifecycle
fixes, plugin dispose/cleanup, cloud sync hardening, global search
mathjs sandbox, and settings storage fixes.

src/seqta/utils/Openers/OpenPrivacyNotification.ts

@@ -62,12 +62,13 @@ export function showPrivacyNotification(onDismissed?: () => void) {
 
   attachPopupMediaFullscreenIfPresent(text, "img.aboutImg");
 
-  settingsState.privacyStatementLastUpdated = "2025-12-20";
-  settingsState.privacyStatementShown = true;
-
   openPopup({
     header,
     content: [text],
-    afterClose: onDismissed,
+    afterClose: () => {
+      settingsState.privacyStatementLastUpdated = "2025-12-20";
+      settingsState.privacyStatementShown = true;
+      onDismissed?.();
+    },
   });
 }