feat: add comprehensive export functionality for palettes

Implement full palette export system with multiple formats:

**Export Utilities (lib/utils/export.ts):**
- exportAsCSS() - CSS custom properties (:root variables)
- exportAsSCSS() - SCSS variables ($color-name format)
- exportAsTailwind() - Tailwind config module export
- exportAsJSON() - Structured JSON with color objects
- exportAsJavaScript() - JavaScript array of colors
- downloadAsFile() - Browser download helper
- ExportColor interface for typed exports

**ExportMenu Component:**
- Format selector dropdown (5 formats)
- Live preview of export code
- Syntax-highlighted code display
- Copy to clipboard button
- Download as file button
- Success feedback (Check icon + toast)
- Responsive layout
- Conditional rendering (empty state)

**Export Formats:**

1. CSS Variables:
   ```css
   :root {
     --color-1: #ff0099;
     --color-2: #0099ff;
   }
   ```

2. SCSS Variables:
   ```scss
   $color-1: #ff0099;
   $color-2: #0099ff;
   ```

3. Tailwind Config:
   ```js
   module.exports = {
     theme: {
       extend: {
         colors: {
           'color-1': '#ff0099',
         },
       },
     },
   };
   ```

4. JSON:
   ```json
   {
     "colors": [
       { "name": "color-1", "hex": "#ff0099" }
     ]
   }
   ```

5. JavaScript Array:
   ```js
   const colors = ['#ff0099', '#0099ff'];
   ```

**Integration:**
- Added to Gradient Creator page
- Added to Distinct Colors page
- Conditional rendering (shows only when colors exist)
- Proper spacing and layout

**Features:**
- Real-time preview of generated code
- Copy with toast notification
- Download with proper file extensions
- Format-specific filenames
- Clean, readable output
- Proper indentation and formatting

**User Experience:**
- Select format from dropdown
- See live preview immediately
- One-click copy or download
- Success feedback
- Professional code formatting

Build successful! Export functionality working on all palette pages.

Next: Keyboard shortcuts and URL sharing.

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

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

app/palettes/gradient/page.tsx

@@ -3,6 +3,7 @@
 import { useState } from 'react';
 import { ColorPicker } from '@/components/color/ColorPicker';
 import { PaletteGrid } from '@/components/color/PaletteGrid';
+import { ExportMenu } from '@/components/tools/ExportMenu';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Select } from '@/components/ui/select';
@@ -173,6 +174,10 @@ export default function GradientPage() {
                   </h2>
                   <PaletteGrid colors={gradient} />
                 </div>
+
+                <div className="p-6 border rounded-lg bg-card">
+                  <ExportMenu colors={gradient} />
+                </div>
               </>
             )}
           </div>