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/Select.tsx

@@ -18,7 +18,7 @@ const Select = React.forwardRef<HTMLSelectElement, SelectProps>(
         )}
         <select
           className={cn(
-            'flex h-10 w-full rounded-xl border border-white/10 bg-white/5 px-3 py-2',
+            'flex h-10 w-full rounded-xl border border-border bg-input px-3 py-2',
             'text-sm ring-offset-background',
             'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary/50 focus-visible:border-primary/50',
             'disabled:cursor-not-allowed disabled:opacity-50 transition-all duration-200',