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>

app/page.tsx

@@ -0,0 +1,45 @@
+export default function HomePage() {
+  return (
+    <main className="flex min-h-screen flex-col items-center justify-center bg-background p-8">
+      <div className="max-w-2xl space-y-6 text-center">
+        <h1 className="text-6xl font-bold bg-gradient-to-r from-primary via-accent to-primary bg-clip-text text-transparent">
+          Paint UI
+        </h1>
+        <p className="text-xl text-muted-foreground">
+          Modern browser-based image editor
+        </p>
+        <div className="grid grid-cols-2 gap-4 pt-8 text-left">
+          <div className="space-y-2 rounded-lg border border-border bg-card p-4">
+            <h3 className="font-semibold text-card-foreground">Phase 1: Foundation</h3>
+            <ul className="space-y-1 text-sm text-muted-foreground">
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> Next.js 16 setup
+              </li>
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> Tailwind CSS 4
+              </li>
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> TypeScript config
+              </li>
+              <li className="flex items-center gap-2">
+                <span className="text-success">✓</span> Theme system
+              </li>
+            </ul>
+          </div>
+          <div className="space-y-2 rounded-lg border border-border bg-card p-4">
+            <h3 className="font-semibold text-card-foreground">Coming Soon</h3>
+            <ul className="space-y-1 text-sm text-muted-foreground">
+              <li>Canvas rendering</li>
+              <li>Layer system</li>
+              <li>Drawing tools</li>
+              <li>Effects & filters</li>
+            </ul>
+          </div>
+        </div>
+        <p className="pt-4 text-sm text-muted-foreground">
+          Built with Next.js 16 • React 19 • Tailwind CSS 4
+        </p>
+      </div>
+    </main>
+  );
+}