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/layout/AppSidebar.tsx

@@ -74,12 +74,12 @@ const navigation: NavGroup[] = [
         href: '/pastel', 
         icon: <PastelIcon className="h-4 w-4" />,
         items: [
-          { title: 'Harmony Palettes', href: '/pastel/palettes/harmony' },
-          { title: 'Distinct Colors', href: '/pastel/palettes/distinct' },
-          { title: 'Gradients', href: '/pastel/palettes/gradient' },
-          { title: 'Contrast Checker', href: '/pastel/accessibility/contrast' },
-          { title: 'Color Blindness', href: '/pastel/accessibility/colorblind' },
-          { title: 'Text Color', href: '/pastel/accessibility/textcolor' },
+          { title: 'Harmony Palettes', href: '/pastel/harmony' },
+          { title: 'Distinct Colors', href: '/pastel/distinct' },
+          { title: 'Gradients', href: '/pastel/gradient' },
+          { title: 'Contrast Checker', href: '/pastel/contrast' },
+          { title: 'Color Blindness', href: '/pastel/colorblind' },
+          { title: 'Text Color', href: '/pastel/textcolor' },
           { title: 'Named Colors', href: '/pastel/names' },
           { title: 'Batch Operations', href: '/pastel/batch' },
         ]