feat: Implement User Registration App - CCSRE-4533

[bdotte]

Summary

Implements the user registration web application as specified in CCSRE-4533.

Requirements Implemented

• ✅ Form with First Name (required), Last Name (required), and Email Address (required)
• ✅ After form submission, display a list of registered users
• ✅ Provide a button to add more users

Features

• Form Validation: Real-time validation with error messages
• Email Validation: Proper email format checking
• XSS Prevention: HTML escaping for user input
• Responsive Design: Clean, accessible UI
• Comprehensive Tests: 21 tests covering all functionality

Test Results

Test Suites: 1 passed, 1 total
Tests:       21 passed, 21 total

How to Test

1. Install dependencies: npm install
2. Run tests: npm test
3. Start server: npm start
4. Open http://localhost:3000

Screenshots

The app provides:

• A clean registration form with validation
• User list display after submission
• "Add More Users" button for additional registrations

Jira Reference

CCSRE-4533: Copilot Jira Integration Test