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>

package.json

@@ -0,0 +1,26 @@
+{
+  "name": "units-ui",
+  "version": "1.0.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev --turbopack",
+    "build": "next build",
+    "start": "next start",
+    "lint": "next lint"
+  },
+  "dependencies": {
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
+    "next": "^16.0.0",
+    "convert-units": "^2.3.4"
+  },
+  "devDependencies": {
+    "typescript": "^5",
+    "@types/node": "^22",
+    "@types/react": "^19",
+    "@types/react-dom": "^19",
+    "tailwindcss": "^4.0.0",
+    "eslint": "^9",
+    "eslint-config-next": "^16.0.0"
+  }
+}