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/figlet/hooks/useKeyboardShortcuts.ts

@@ -0,0 +1,34 @@
+'use client';
+
+import { useEffect } from 'react';
+
+export interface KeyboardShortcut {
+  key: string;
+  ctrlKey?: boolean;
+  metaKey?: boolean;
+  shiftKey?: boolean;
+  handler: () => void;
+  description: string;
+}
+
+export function useKeyboardShortcuts(shortcuts: KeyboardShortcut[]) {
+  useEffect(() => {
+    const handleKeyDown = (event: KeyboardEvent) => {
+      for (const shortcut of shortcuts) {
+        const keyMatches = event.key.toLowerCase() === shortcut.key.toLowerCase();
+        const ctrlMatches = shortcut.ctrlKey ? event.ctrlKey || event.metaKey : !event.ctrlKey && !event.metaKey;
+        const metaMatches = shortcut.metaKey ? event.metaKey : true;
+        const shiftMatches = shortcut.shiftKey ? event.shiftKey : !event.shiftKey;
+
+        if (keyMatches && ctrlMatches && shiftMatches) {
+          event.preventDefault();
+          shortcut.handler();
+          break;
+        }
+      }
+    };
+
+    window.addEventListener('keydown', handleKeyDown);
+    return () => window.removeEventListener('keydown', handleKeyDown);
+  }, [shortcuts]);
+}