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/Footer.tsx

@@ -24,17 +24,17 @@ export function Footer() {
             <h3 className="font-semibold">Resources</h3>
             <ul className="space-y-2 text-sm">
               <li>
-                <Link href="/pastel/playground" className="text-muted-foreground hover:text-foreground transition-colors">
+                <Link href="/pastel" className="text-muted-foreground hover:text-foreground transition-colors">
                   Color Playground
                 </Link>
               </li>
               <li>
-                <Link href="/pastel/palettes" className="text-muted-foreground hover:text-foreground transition-colors">
+                <Link href="/pastel/harmony" className="text-muted-foreground hover:text-foreground transition-colors">
                   Palette Generator
                 </Link>
               </li>
               <li>
-                <Link href="/pastel/accessibility" className="text-muted-foreground hover:text-foreground transition-colors">
+                <Link href="/pastel/contrast" className="text-muted-foreground hover:text-foreground transition-colors">
                   Accessibility Tools
                 </Link>
               </li>