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/figlet/TextInput.tsx

@@ -17,7 +17,7 @@ export function TextInput({ value, onChange, placeholder, className }: TextInput
         value={value}
         onChange={(e) => onChange(e.target.value)}
         placeholder={placeholder || 'Type something...'}
-        className="w-full h-32 px-4 py-3 text-base border border-input rounded-lg bg-background resize-none focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 placeholder:text-muted-foreground"
+        className="w-full h-32 px-4 py-3 text-base border border-border rounded-lg bg-input resize-none focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring placeholder:text-muted-foreground transition-all duration-200"
         maxLength={100}
       />
       <div className="absolute bottom-2 right-2 text-xs text-muted-foreground">