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/batch/page.tsx

@@ -106,7 +106,7 @@ export default function BatchPage() {
                 value={inputColors}
                 onChange={(e) => setInputColors(e.target.value)}
                 placeholder="#ff0099, #00ff99, #9900ff
#ff5533
#3355ff"
-                className="w-full h-48 p-3 border rounded-lg bg-background font-mono text-sm"
+                className="w-full h-48 p-3 border border-border rounded-xl bg-input font-mono text-sm focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary/50 focus-visible:border-primary/50 transition-all duration-200"
               />
 
               <p className="text-xs text-muted-foreground mt-2">

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>
+    </>
   );
 }