feat: initialize Next.js 16 project with TypeScript and Tailwind CSS 4

Set up complete Next.js 16 development environment:
- Next.js 16.0.1 with App Router and Turbopack
- React 19.2.0 with TypeScript 5.9
- Tailwind CSS 4.1.17 with custom category colors
- ESLint 9 with Next.js config
- Static site generation enabled (output: 'export')

Project structure:
- app/ directory with layout, page, and globals.css
- Tailwind config with 23 category-specific colors
- TypeScript config with strict mode and path aliases
- Complete .gitignore for Next.js projects

Dependencies installed:
- convert-units 2.3.4 for unit conversions
- All React 19 and Next.js 16 dependencies
- Development tooling (TypeScript, ESLint, Tailwind)

Ready for Phase 2: Core conversion engine implementation

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

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

app/globals.css

@@ -0,0 +1 @@
+@import "tailwindcss";