feat: migrate ESLint to v9 flat config

- Replace .eslintrc.json with eslint.config.mjs
- Simplify configuration using @antfu/eslint-config
- Add necessary ESLint plugin dependencies
- Disable overly strict style rules
- Set package.json type to module for ESM support
- Fix ESLint disable comment format

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/components/header.tsx

@@ -5,7 +5,7 @@ import {
   PencilSquareIcon,
 } from '@heroicons/react/24/solid'
 import AppIcon from '@/app/components/base/app-icon'
-export type IHeaderProps = {
+export interface IHeaderProps {
   title: string
   isMobile?: boolean
   onShowSideBar?: () => void
@@ -35,9 +35,7 @@ const Header: FC<IHeaderProps> = ({
       </div>
       {isMobile
         ? (
-          <div className='flex items-center justify-center h-8 w-8 cursor-pointer'
-            onClick={() => onCreateNewChat?.()}
-          >
+          <div className='flex items-center justify-center h-8 w-8 cursor-pointer' onClick={() => onCreateNewChat?.()} >
             <PencilSquareIcon className="h-4 w-4 text-gray-500" />
           </div>)
         : <div></div>}