feat: implement Figlet, Pastel, and Unit tools with a unified layout

- Add Figlet text converter with font selection and history
- Add Pastel color palette generator and manipulation suite
- Add comprehensive Units converter with category-based logic
- Introduce AppShell with Sidebar and Header for navigation
- Modernize theme system with CSS variables and new animations
- Update project configuration and dependencies

components/providers/Providers.tsx

@@ -0,0 +1,32 @@
+'use client';
+
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { Toaster } from 'sonner';
+import { useState } from 'react';
+import { ThemeProvider } from './ThemeProvider';
+import { ToastProvider } from '@/components/ui/Toast';
+
+export function Providers({ children }: { children: React.ReactNode }) {
+  const [queryClient] = useState(
+    () =>
+      new QueryClient({
+        defaultOptions: {
+          queries: {
+            staleTime: 60 * 1000, // 1 minute
+            refetchOnWindowFocus: false,
+          },
+        },
+      })
+  );
+
+  return (
+    <ThemeProvider>
+      <ToastProvider>
+        <QueryClientProvider client={queryClient}>
+          {children}
+          <Toaster position="top-right" richColors />
+        </QueryClientProvider>
+      </ToastProvider>
+    </ThemeProvider>
+  );
+}