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/utils/debounce.ts

@@ -0,0 +1,18 @@
+export function debounce<T extends (...args: any[]) => any>(
+  func: T,
+  wait: number
+): (...args: Parameters<T>) => void {
+  let timeout: NodeJS.Timeout | null = null;
+
+  return function executedFunction(...args: Parameters<T>) {
+    const later = () => {
+      timeout = null;
+      func(...args);
+    };
+
+    if (timeout) {
+      clearTimeout(timeout);
+    }
+    timeout = setTimeout(later, wait);
+  };
+}