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>

tailwind.config.ts

@@ -0,0 +1,44 @@
+import type { Config } from 'tailwindcss';
+
+const config: Config = {
+  content: [
+    './pages/**/*.{js,ts,jsx,tsx,mdx}',
+    './components/**/*.{js,ts,jsx,tsx,mdx}',
+    './app/**/*.{js,ts,jsx,tsx,mdx}',
+  ],
+  theme: {
+    extend: {
+      colors: {
+        // Category colors for 23 unit types
+        category: {
+          angle: '#0EA5E9',
+          'apparent-power': '#8B5CF6',
+          area: '#F59E0B',
+          current: '#F59E0B',
+          digital: '#06B6D4',
+          each: '#64748B',
+          energy: '#EAB308',
+          frequency: '#A855F7',
+          illuminance: '#84CC16',
+          length: '#3B82F6',
+          mass: '#10B981',
+          pace: '#14B8A6',
+          'parts-per': '#EC4899',
+          power: '#F43F5E',
+          pressure: '#6366F1',
+          'reactive-energy': '#D946EF',
+          'reactive-power': '#E879F9',
+          speed: '#10B981',
+          temperature: '#EF4444',
+          time: '#7C3AED',
+          voltage: '#FB923C',
+          volume: '#8B5CF6',
+          'volume-flow-rate': '#22D3EE',
+        },
+      },
+    },
+  },
+  plugins: [],
+};
+
+export default config;