feat: implement palette generation features

Add complete palette generation system with multiple methods:

**New Components:**
- ColorSwatch component - Individual color display
  - Click to copy to clipboard
  - Hover effects with copy icon
  - Configurable sizes (sm, md, lg)
  - Optional color label display
  - Check icon on successful copy

- PaletteGrid component - Grid display for color palettes
  - Responsive grid layout (3-6 columns)
  - Click handler for color selection
  - Empty state message
  - Flexible and reusable

- Select component - Dropdown selector
  - Consistent styling with other inputs
  - Optional label support
  - Keyboard accessible
  - Focus ring styling

**Palette Pages:**

1. Gradient Creator (/palettes/gradient)
   - Multiple color stop editor (add/remove)
   - Configurable step count (2-1000)
   - Color space selection (RGB, HSL, Lab, LCH, OkLab, OkLCH)
   - Live gradient preview bar
   - Full palette grid display
   - Interactive color pickers for each stop
   - Real-time generation

2. Distinct Colors (/palettes/distinct)
   - Count selector (2-100 colors)
   - Distance metric selection (CIE76, CIEDE2000)
   - Simulated annealing algorithm
   - Statistics display:
     - Minimum distance
     - Average distance
     - Generation time
   - Loading state with progress message
   - Quality metrics for generated palette

3. Palettes Dashboard (/palettes)
   - Overview of all palette generators
   - Feature cards with icons
   - "Coming Soon" badge for harmony palettes
   - Quick navigation to each generator
   - Feature highlights for each method

**Features:**
- All palette generators integrated with Pastel API
- Toast notifications for success/error
- Loading states during generation
- Copy colors to clipboard
- Responsive layouts
- Empty states
- Error handling

**API Integration:**
- useGenerateGradient mutation
- useGenerateDistinct mutation
- Proper error handling and loading states
- Result caching with React Query

Build successful! 3 new palette pages rendering.

Next: Harmony palettes, accessibility tools, and named colors.

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

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

components/color/ColorSwatch.tsx

@@ -0,0 +1,65 @@
+'use client';
+
+import { cn } from '@/lib/utils/cn';
+import { Check, Copy } from 'lucide-react';
+import { useState } from 'react';
+import { toast } from 'sonner';
+
+interface ColorSwatchProps {
+  color: string;
+  size?: 'sm' | 'md' | 'lg';
+  showLabel?: boolean;
+  onClick?: () => void;
+  className?: string;
+}
+
+export function ColorSwatch({
+  color,
+  size = 'md',
+  showLabel = true,
+  onClick,
+  className,
+}: ColorSwatchProps) {
+  const [copied, setCopied] = useState(false);
+
+  const sizeClasses = {
+    sm: 'h-12 w-12',
+    md: 'h-16 w-16',
+    lg: 'h-24 w-24',
+  };
+
+  const handleCopy = (e: React.MouseEvent) => {
+    e.stopPropagation();
+    navigator.clipboard.writeText(color);
+    setCopied(true);
+    toast.success(`Copied ${color}`);
+    setTimeout(() => setCopied(false), 2000);
+  };
+
+  return (
+    <div className={cn('flex flex-col items-center gap-2', className)}>
+      <button
+        className={cn(
+          'relative rounded-lg ring-2 ring-border transition-all hover:scale-105 hover:ring-primary',
+          'focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2',
+          'group',
+          sizeClasses[size]
+        )}
+        style={{ backgroundColor: color }}
+        onClick={onClick || handleCopy}
+        aria-label={`Color ${color}`}
+      >
+        <div className="absolute inset-0 flex items-center justify-center opacity-0 group-hover:opacity-100 transition-opacity bg-black/20 rounded-lg">
+          {copied ? (
+            <Check className="h-5 w-5 text-white" />
+          ) : (
+            <Copy className="h-5 w-5 text-white" />
+          )}
+        </div>
+      </button>
+      {showLabel && (
+        <span className="text-xs font-mono text-muted-foreground">{color}</span>
+      )}
+    </div>
+  );
+}

components/color/PaletteGrid.tsx

@@ -0,0 +1,37 @@
+'use client';
+
+import { ColorSwatch } from './ColorSwatch';
+import { cn } from '@/lib/utils/cn';
+
+interface PaletteGridProps {
+  colors: string[];
+  onColorClick?: (color: string) => void;
+  className?: string;
+}
+
+export function PaletteGrid({ colors, onColorClick, className }: PaletteGridProps) {
+  if (colors.length === 0) {
+    return (
+      <div className="text-center py-12 text-muted-foreground">
+        No colors in palette yet
+      </div>
+    );
+  }
+
+  return (
+    <div
+      className={cn(
+        'grid grid-cols-3 sm:grid-cols-4 md:grid-cols-5 lg:grid-cols-6 gap-4',
+        className
+      )}
+    >
+      {colors.map((color, index) => (
+        <ColorSwatch
+          key={`${color}-${index}`}
+          color={color}
+          onClick={onColorClick ? () => onColorClick(color) : undefined}
+        />
+      ))}
+    </div>
+  );
+}

components/ui/select.tsx

@@ -0,0 +1,39 @@
+'use client';
+
+import * as React from 'react';
+import { cn } from '@/lib/utils/cn';
+
+export interface SelectProps extends React.SelectHTMLAttributes<HTMLSelectElement> {
+  label?: string;
+}
+
+const Select = React.forwardRef<HTMLSelectElement, SelectProps>(
+  ({ className, label, children, ...props }, ref) => {
+    return (
+      <div className="space-y-2">
+        {label && (
+          <label htmlFor={props.id} className="text-sm font-medium">
+            {label}
+          </label>
+        )}
+        <select
+          className={cn(
+            'flex h-10 w-full rounded-md border border-input bg-background px-3 py-2',
+            'text-sm ring-offset-background',
+            'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring',
+            'disabled:cursor-not-allowed disabled:opacity-50',
+            className
+          )}
+          ref={ref}
+          {...props}
+        >
+          {children}
+        </select>
+      </div>
+    );
+  }
+);
+
+Select.displayName = 'Select';
+
+export { Select };