feat: enhance bottom tabs with search functionality

[JorFlux]

• Added searchable boolean property to route options
• Added navigationBarToolbarStyle property to control navigation bar toolbar visibility ('automatic' | 'hidden' | 'visible')
• Added onSearchTextChange callback that fires when search text changes
• Added onSearchFocusChange callback that fires when search field gains/loses focus
• Created RepresentableViewController wrapper to properly integrate UIViewController with SwiftUI NavigationView (required for searchable functionality)
• Updated iOS implementation to conditionally wrap searchable tabs in NavigationView and apply .searchable() modifier
• Added support for both direct TabView usage and React Navigation integration

How to test?

1. Using TabView directly:

   <TabView
     navigationState={{ index, routes }}
     onIndexChange={setIndex}
     renderScene={renderScene}
     onSearchTextChange={(text) => console.log('Search text:', text)}
     onSearchFocusChange={(isFocused) => console.log('Search focused:', isFocused)}
   />
   
   // In your routes:
   {
     key: 'contacts',
     title: 'Contacts',
     searchable: true,
     navigationBarToolbarStyle: 'visible', // or 'hidden' or 'automatic'
   }

2. Using React Navigation:

   <Tab.Navigator
     onSearchTextChange={(text) => console.log('Search text:', text)}
     onSearchFocusChange={(isFocused) =>
       console.log('Search focused:', isFocused)
     }
   >
     <Tab.Screen
       name="Contacts"
       component={ContactsScreen}
       options={{
         searchable: true,
         navigationBarToolbarStyle: 'visible',
       }}
     />
   </Tab.Navigator>

Screenshots

For iOS 26 and higher

For iOS 18