feat: complete Phase 1 - project foundation with Next.js 16 and Tailwind CSS 4

Initialize modern tech stack following audio-ui patterns:

**Framework Setup**
- Next.js 16 with App Router and Turbopack (ready in 754ms)
- React 19 with TypeScript 5
- Static export configuration for deployment

**Styling System**
- Tailwind CSS 4 with @tailwindcss/postcss
- OKLCH color space for vibrant, perceptually uniform colors
- Custom CSS variables for theming (light/dark modes)
- Canvas-specific color palette (canvas-bg, canvas-grid, canvas-selection)
- Custom animations (fadeIn, slideDown, scaleIn, etc.)
- Checkerboard pattern utility for transparency preview
- Custom scrollbar styling

**State Management**
- Zustand installed for layers, canvas, and history state

**Canvas Libraries**
- pica for high-quality image resizing
- file-saver for export functionality
- uuid for layer ID generation

**Development Experience**
- Path aliases (@/* pattern) configured
- Strict TypeScript with proper type checking
- Auto dark mode detection with localStorage persistence
- Responsive layout with overflow handling

**Initial UI**
- Root layout with theme system
- Landing page showing Phase 1 completion status
- Clean, modern design with gradient title

Ready for Phase 2: Core Canvas Engine implementation.

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

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

postcss.config.js

@@ -0,0 +1,8 @@
+/** @type {import('postcss-load-config').Config} */
+const config = {
+  plugins: {
+    '@tailwindcss/postcss': {},
+  },
+};
+
+module.exports = config;