Flutter – Why my output have no Image and heading in all red with double yellow underline along with black background?

import 'package:flutter/material.dart';

class SiginupPage extends StatefulWidget {
  const SiginupPage({super.key});

  @override
  State<SiginupPage> createState() => _SiginupPageState();
}

class _SiginupPageState extends State<SiginupPage> {
  @override
  Widget build(BuildContext context) {
    return SafeArea(child: Container(
      width: double.infinity,
      height: MediaQuery.of(context).size.height,
      padding: const EdgeInsets.symmetric(horizontal: 30,vertical: 30),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              const Text(
                'Get Started',
                style: TextStyle(fontWeight: FontWeight.bold,fontSize: 40),
              ),
              const SizedBox(height: 30,),
              Text('Hey lets get started with this journey to development',
              textAlign: TextAlign.center,
              style: TextStyle(
                color: Colors.grey[700],
                fontSize: 15
              ),
              ),
            ],
          ),
          Container(
            height: MediaQuery.of(context).size.height/3,
            decoration: const BoxDecoration(
              image: DecorationImage(
                  image: AssetImage('lib/assets/image/1stbg.png')
              ),
            ),
          )
        ],
      ),
    ));
  }
}

enter image description here

Why my output have no Image and heading in all red with double yellow underline along with black background ?i want it to appear with all default background with default color of heading with no underline and my image must render