Fix missing `setTimeout` cleanup in onboarding tour retry logic

[MODSetter]

Description

The onboarding tour component uses recursive setTimeout calls to retry finding target elements, but only the initial setTimeout is cleaned up on unmount. The inner retry setTimeout calls (line ~575, ~480) are never cancelled, which can cause state updates on unmounted components.

Files to Update

• surfsense_web/components/onboarding-tour.tsx (lines ~558–581 and ~478–488)

What to Do

Use a ref to track whether the effect is still active, and skip state updates after cleanup:

// For the checkAndStartTour retry pattern (lines ~558-581):
useEffect(() => {
  let cancelled = false;

  const checkAndStartTour = () => {
    if (cancelled) return;
    
    const connectorEl = document.querySelector(...);
    // ...
    if (connectorEl && documentsEl && inboxEl) {
      // start tour
    } else {
      setTimeout(checkAndStartTour, 200);  // recursive retry
    }
  };

  const timer = setTimeout(checkAndStartTour, 500);
  return () => {
    cancelled = true;
    clearTimeout(timer);
  };
}, [/* deps */]);

Apply the same cancelled flag pattern to the updateTarget retry logic (lines ~478–488). The flag ensures that after cleanup, no further setTimeout callbacks will attempt DOM queries or state updates.

[LikiosSedo]

I'd like to take this one.