refactor: flatten Pastel routes by removing intermediate palettes and accessibility paths

- Move sub-routes from /pastel/palettes/* and /pastel/accessibility/* to direct children of /pastel
- Update AppSidebar navigation links
- Update Pastel Navbar and Footer links
- Update Tailwind source directives in pastel/globals.css
- Remove intermediate page files

components/pastel/layout/Navbar.tsx

@@ -7,11 +7,10 @@ import { cn } from '@/lib/utils/cn';
 import { Palette } from 'lucide-react';
 
 const navigation = [
-  { name: 'Home', href: '/pastel' },
-  { name: 'Playground', href: '/pastel/playground' },
-  { name: 'Palettes', href: '/pastel/palettes' },
-  { name: 'Accessibility', href: '/pastel/accessibility' },
-  { name: 'Named Colors', href: '/pastel/names' },
+  { name: 'Playground', href: '/pastel' },
+  { name: 'Harmony', href: '/pastel/harmony' },
+  { name: 'Contrast', href: '/pastel/contrast' },
+  { name: 'Names', href: '/pastel/names' },
   { name: 'Batch', href: '/pastel/batch' },
 ];