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

lib/storage/favorites.ts

@@ -0,0 +1,70 @@
+'use client';
+
+const FAVORITES_KEY = 'figlet-ui-favorites';
+const RECENT_FONTS_KEY = 'figlet-ui-recent-fonts';
+const MAX_RECENT = 10;
+
+export function getFavorites(): string[] {
+  if (typeof window === 'undefined') return [];
+
+  try {
+    const stored = localStorage.getItem(FAVORITES_KEY);
+    return stored ? JSON.parse(stored) : [];
+  } catch {
+    return [];
+  }
+}
+
+export function addFavorite(fontName: string): void {
+  const favorites = getFavorites();
+  if (!favorites.includes(fontName)) {
+    favorites.push(fontName);
+    localStorage.setItem(FAVORITES_KEY, JSON.stringify(favorites));
+  }
+}
+
+export function removeFavorite(fontName: string): void {
+  const favorites = getFavorites();
+  const filtered = favorites.filter(f => f !== fontName);
+  localStorage.setItem(FAVORITES_KEY, JSON.stringify(filtered));
+}
+
+export function isFavorite(fontName: string): boolean {
+  return getFavorites().includes(fontName);
+}
+
+export function toggleFavorite(fontName: string): boolean {
+  const isCurrentlyFavorite = isFavorite(fontName);
+  if (isCurrentlyFavorite) {
+    removeFavorite(fontName);
+  } else {
+    addFavorite(fontName);
+  }
+  return !isCurrentlyFavorite;
+}
+
+export function getRecentFonts(): string[] {
+  if (typeof window === 'undefined') return [];
+
+  try {
+    const stored = localStorage.getItem(RECENT_FONTS_KEY);
+    return stored ? JSON.parse(stored) : [];
+  } catch {
+    return [];
+  }
+}
+
+export function addRecentFont(fontName: string): void {
+  let recent = getRecentFonts();
+
+  // Remove if already exists
+  recent = recent.filter(f => f !== fontName);
+
+  // Add to beginning
+  recent.unshift(fontName);
+
+  // Keep only MAX_RECENT items
+  recent = recent.slice(0, MAX_RECENT);
+
+  localStorage.setItem(RECENT_FONTS_KEY, JSON.stringify(recent));
+}