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

components/ui/Card.tsx

@@ -5,7 +5,7 @@ const Card = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElemen
   ({ className, ...props }, ref) => (
     <div
       ref={ref}
-      className={cn('glass rounded-2xl text-card-foreground shadow-xl transition-all duration-300', className)}
+      className={cn('bg-card text-card-foreground border rounded-lg transition-all duration-300', className)}
       {...props}
     />
   )