feat: smooth navigation transitions + config updates

- Migrate MainStack from JS stack to native-stack for native-thread,
  jank-free screen transitions (slide_from_right, fade for auth screens)
- Add shift animation to bottom tab switching
- Install @react-navigation/native-stack
- Update API URLs, Axios, Login and Android network security config

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/Navigation/Bottom.tsx

@@ -193,6 +193,8 @@ export default function BottomTab() {
                 screenOptions={{
                     headerShown: false,
                     tabBarHideOnKeyboard: true,
+                    // Smooth cross-fade when switching tabs instead of an instant cut.
+                    animation: 'shift',
                 }}
             >
                 <Tab.Screen name="Home" component={Screens.Home} />