Create missing index.html file in public directory to fix React app build

[Copilot]

This PR fixes a critical build issue where the React application was missing the required index.html template file in the public directory. This file is essential for Create React App projects as it serves as the HTML template that React uses to mount the application.

Problem

The project was failing to build with the error:

Could not find a required file.
  Name: index.html
  Searched in: /home/runner/work/MedXAI-UI/MedXAI-UI/public

Solution

Created a properly structured index.html file in the public directory that includes:

• Standard HTML5 doctype and structure
• React-specific root div element (<div id="root"></div>) where the application mounts
• Proper meta tags for viewport, theme color, and SEO description
• Create React App placeholder tokens (%PUBLIC_URL%) for asset references
• Links to favicon, app icons, and manifest for PWA functionality

Additional Fixes

Since the project had missing React components that were being imported, this PR also:

• Created the missing src/views/Index.js component that was referenced in App.js
• Updated App.test.js to test for the correct content instead of placeholder text

Verification

• ✅ npm run build now completes successfully
• ✅ npm start launches the development server without errors
• ✅ All unit tests pass
• ✅ Production build generates optimized assets correctly

The application is now fully functional and ready for development and deployment.

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