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>
+  );
+}

components/providers/ThemeProvider.tsx

@@ -0,0 +1,78 @@
+'use client';
+
+import { createContext, useContext, useEffect, useState } from 'react';
+
+type Theme = 'light' | 'dark' | 'system';
+
+interface ThemeContextType {
+  theme: Theme;
+  setTheme: (theme: Theme) => void;
+  resolvedTheme: 'light' | 'dark';
+}
+
+const ThemeContext = createContext<ThemeContextType | undefined>(undefined);
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const [theme, setTheme] = useState<Theme>('dark');
+  const [resolvedTheme, setResolvedTheme] = useState<'light' | 'dark'>('dark');
+
+  useEffect(() => {
+    // Load theme from localStorage
+    const stored = localStorage.getItem('theme') as Theme | null;
+    if (stored) {
+      setTheme(stored);
+    }
+  }, []);
+
+  useEffect(() => {
+    const root = window.document.documentElement;
+
+    // Remove previous theme classes
+    root.classList.remove('light', 'dark');
+
+    if (theme === 'system') {
+      const systemTheme = window.matchMedia('(prefers-color-scheme: dark)').matches
+        ? 'dark'
+        : 'light';
+      root.classList.add(systemTheme);
+      setResolvedTheme(systemTheme);
+    } else {
+      root.classList.add(theme);
+      setResolvedTheme(theme);
+    }
+
+    // Save to localStorage
+    localStorage.setItem('theme', theme);
+  }, [theme]);
+
+  // Listen for system theme changes
+  useEffect(() => {
+    const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
+
+    const handleChange = () => {
+      if (theme === 'system') {
+        const systemTheme = mediaQuery.matches ? 'dark' : 'light';
+        setResolvedTheme(systemTheme);
+        window.document.documentElement.classList.remove('light', 'dark');
+        window.document.documentElement.classList.add(systemTheme);
+      }
+    };
+
+    mediaQuery.addEventListener('change', handleChange);
+    return () => mediaQuery.removeEventListener('change', handleChange);
+  }, [theme]);
+
+  return (
+    <ThemeContext.Provider value={{ theme, setTheme, resolvedTheme }}>
+      {children}
+    </ThemeContext.Provider>
+  );
+}
+
+export function useTheme() {
+  const context = useContext(ThemeContext);
+  if (context === undefined) {
+    throw new Error('useTheme must be used within a ThemeProvider');
+  }
+  return context;
+}