perf: remove navbar remount key & add passive scroll/touch listeners

- Remove key={String(open)} from MobileNav container to prevent
  unnecessary full DOM remounts on every menu toggle (fixes #1098)
  The animate prop already handles border-radius transitions via
  Framer Motion so the key prop was redundant
- Add { passive: true } to all scroll and touch event listeners
  (fixes #1053)
  window.addEventListener('scroll') in Navbar and MobileNav
  document.addEventListener('touchstart') in click-outside handler
  window.addEventListener('scroll', true) in onboarding-tour (uses
  capture + passive since handlers only read geometry, no preventDefault)

surfsense_web/components/onboarding-tour.tsx

@@ -598,7 +598,7 @@ export function OnboardingTour() {
 		};
 
 		window.addEventListener("resize", handleUpdate);
-		window.addEventListener("scroll", handleUpdate, true);
+		window.addEventListener("scroll", handleUpdate, { capture: true, passive: true });
 
 		return () => {
 			window.removeEventListener("resize", handleUpdate);