How to border radius to navigation bar flutter

curly_bottom_navbar.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with TickerProviderStateMixin {
  late TabController _tabController;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: 4, vsync: this);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      bottomNavigationBar: DefaultTabController(
        length: 4,
        initialIndex: 0,
        child: Container(
          margin: const EdgeInsets.only(bottom: .5),
          padding: const EdgeInsets.only(top: 3),
          height: 50,
          decoration: BoxDecoration(
            // color: Theme.of(context).backgroundColor,
            color: Colors.white,
            border: Border.all(
              color: Colors.grey[700]!,
              width: 0.5,
            ),
            borderRadius: const BorderRadius.only(
              topRight: Radius.circular(17),
              topLeft: Radius.circular(17),
            ),
          ),
          child: TabBar(
            physics: const NeverScrollableScrollPhysics(),
            isScrollable: false,

            controller: _tabController,
            indicatorWeight: 0,
            // mouseCursor: MouseCursor.defer,
            indicator: const UnderlineTabIndicator(
              borderSide: BorderSide(
                color: Colors.black,
                width: 1,
              ),
              // insets: EdgeInsets.symmetric(horizontal: 0),
            ),
            tabs: [
              kTabBarItemConstructor(
                Icons.home,
                'Home',
              ),
              Container(
                child: kTabBarItemConstructor(
                  Icons.home,
                  'Home',
                ),
              ),
              Container(
                child: kTabBarItemConstructor(
                  Icons.home,
                  'Profile',
                ),
              ),
              // Tab(
              //   child: Container(
              //     child: Column(
              //       mainAxisAlignment: MainAxisAlignment.center,
              //       children: [
              //
              //         Text(
              //           'Корзина',
              //           style: TextStyle(
              //             fontSize: 9,
              //             color: Colors.grey[600],
              //           ),
              //         ),
              //       ],
              //     ),
              //   ),
              // ),
              kTabBarItemConstructor(
                Icons.home,
                'Profile',
              ),
            ],
          ),
        ),
      ),
    ));
  }
}
Widget kTabBarItemConstructor(IconData icon, String text) {
  return Tab(
    child: Container(
      height: 40,
      width: 70,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Icon(
            icon,
            color: Colors.black.withOpacity(.65),
            size: 25,
          ),
          Container(
            // margin: EdgeInsets.symmetric(horizontal: 10),
            child: Text(
              text,
              style: TextStyle(
                fontSize: 9,
                color: Colors.grey[600],
              ),
              maxLines: 1,
              overflow: TextOverflow.ellipsis,
            ),
          ),
        ],
      ),
    ),
  );
}