Implement "Try Demo" feature for Flight Search

Overview

Add a simple "Demo Mode" feature that showcases the app's flight search capabilities with pre-populated sample data for demonstrations.

Feature Requirements

• Add a "Try Demo" button on the main search page
• When clicked, auto-populate search form with sample data:
  • Origin: "New York (NYC)"
  • Destination: "London (LDN)"
  • Departure: Next Monday
  • Return: Following Friday
  • Passengers: 2 adults
• Display mock flight results with realistic but clearly labeled demo data
• Add subtle "Demo Mode" indicator in the UI
• Include a "Exit Demo" option to return to normal search

Implementation Notes

• Keep it simple - no backend changes needed
• Use frontend-only mock data
• Should take 2-4 hours to implement
• Perfect for showcasing the app's UI and user flow during demos

Acceptance Criteria

• Demo button is visible and accessible on main page
• Demo mode populates realistic sample search data
• Mock results display properly formatted flight information
• Demo mode indicator is clearly visible
• Users can easily exit demo mode
• Feature doesn't interfere with normal app functionality