Add responsive Header component with navigation

[Copilot]

This PR adds a professional header component to the Vite + React template, providing better navigation structure and improved user experience.

Changes Made

New Components

• Header Component (src/react-app/components/Header.tsx): A clean, modern header featuring:

  • Branded title "Vite React Template" with descriptive subtitle
  • Navigation links to Vite, React, Hono, and Cloudflare documentation
  • Sticky positioning for persistent access
  • Semantic HTML with proper accessibility attributes

• Header Styling (src/react-app/components/Header.css): Comprehensive responsive styles including:

  • Gradient background matching the existing theme
  • Smooth hover transitions on navigation links
  • Mobile-first responsive design with three breakpoints
  • Light/dark theme support using CSS media queries

Integration

• Updated App.tsx to include the Header component at the top of the layout
• Adjusted App.css root padding to accommodate the new sticky header
• Maintained all existing functionality and styling

Design Features

The header provides a professional navigation experience with:

• Desktop Layout: Side-by-side branding and navigation
• Tablet Layout: Maintained horizontal structure with optimized spacing
• Mobile Layout: Stacked vertical layout with centered content

All navigation links open in new tabs to preserve the user's current session while providing quick access to documentation.

Screenshots

Desktop View:

Tablet View (768px):

Mobile View (375px):

Testing

• ✅ All existing functionality preserved (counter buttons, API calls)
• ✅ TypeScript compilation successful
• ✅ ESLint passes with no new warnings
• ✅ Build process completes successfully
• ✅ Responsive design tested across multiple viewport sizes
• ✅ Navigation links work correctly with proper target="_blank" behavior

The implementation follows React best practices with proper component separation, maintains the existing design language, and adds zero breaking changes to the current functionality.

Fixes #4.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• sparrow.cloudflare.com
  • Triggering command: /usr/local/bin/node --no-warnings --experimental-vm-modules /home/REDACTED/work/vite-react-template/vite-react-template/node_modules/wrangler/wrangler-dist/cli.js deploy --dry-run (dns block)
• workers.cloudflare.com
  • Triggering command: node /home/REDACTED/work/vite-react-template/vite-react-template/node_modules/.bin/vite (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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