refactor: streamline toast system and harmonize UI across tools

- Migrate all toast notifications to sonner and remove custom ToastProvider
- Align Card and TextInput styling across Figlet and Pastel (rounded-lg, border-based)
- Fix build error by removing non-existent export in lib/units/index.ts
- Clean up unused Figlet components and constants

app/(app)/pastel/layout.tsx

@@ -4,8 +4,8 @@ export default function PastelLayout({
   children: React.ReactNode;
 }>) {
   return (
-    <div className="p-4 sm:p-8 max-w-7xl mx-auto">
+    <>
       {children}
-    </div>
+    </>
   );
 }