[Fix] searchBar `focus:` true ignored on mergeOptions when searchController already exists

Bug

When calling Navigation.mergeOptions() with topBar.searchBar.focus: true on a screen that already has a search controller, the focus is silently ignored. The search bar only auto-focuses on initial creation (first applyOptions), never on subsequent mergeOptions calls.

Current Behaviour

setSearchBarWithOptions: in UIViewController+RNNOptions.mm only handles focus inside the if (!self.navigationItem.searchController) branch (initial creation). The else branch (existing search controller) skips focus entirely.

Expected Behaviour

mergeOptions with focus: true should refocus the search bar even when the search controller already exists. This is needed for re-focusing the search bar when the screen reappears (e.g., switching back to a bottom tab).

Steps to Reproduce

1. Register a screen with searchBar: { visible: true, focus: true } in static options
2. Screen mounts — search bar is focused (correct)
3. Navigate away from the screen (e.g., switch tabs)
4. Navigate back and call Navigation.mergeOptions(componentId, { topBar: { searchBar: { visible: true, focus: true } } })
5. Search bar is not focused

Proposed Fix

Add focus handling in the else branch of setSearchBarWithOptions::

} else {
    // ... existing iOS 26 placement code ...

    if (focus) {
        dispatch_async(dispatch_get_main_queue(), ^{
          self.navigationItem.searchController.active = true;
          [self.navigationItem.searchController.searchBar becomeFirstResponder];
        });
    }
}

Environment

• react-native-navigation: 8.8.2
• React Native: 0.85.3
• iOS 18+

Start in UIViewController+RNNOptions.mm at setSearchBarWithOptions:, comparing the existing-controller path with the initial creation path. Verify the mergeOptions flow on a screen with an existing search controller, then run the relevant iOS tests or reproduce the tab-switching steps. Done means focus: true refocuses the search bar after mergeOptions without changing initial creation behavior.