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/pastel/hooks/useKeyboard.ts

@@ -0,0 +1,106 @@
+import { useEffect } from 'react';
+
+export interface KeyboardShortcut {
+  key: string;
+  ctrl?: boolean;
+  shift?: boolean;
+  alt?: boolean;
+  meta?: boolean;
+  handler: (event: KeyboardEvent) => void;
+  description?: string;
+}
+
+/**
+ * Hook to register keyboard shortcuts
+ *
+ * @example
+ * ```tsx
+ * useKeyboard([
+ *   {
+ *     key: 'c',
+ *     meta: true, // Cmd on Mac, Ctrl on Windows
+ *     handler: () => copyToClipboard(),
+ *     description: 'Copy color',
+ *   },
+ *   {
+ *     key: 'k',
+ *     meta: true,
+ *     handler: () => openCommandPalette(),
+ *     description: 'Open command palette',
+ *   },
+ * ]);
+ * ```
+ */
+export function useKeyboard(shortcuts: KeyboardShortcut[]) {
+  useEffect(() => {
+    const handleKeyDown = (event: KeyboardEvent) => {
+      for (const shortcut of shortcuts) {
+        const keyMatches = event.key.toLowerCase() === shortcut.key.toLowerCase();
+
+        // Check if required modifiers match (only check if explicitly required)
+        const ctrlMatches = shortcut.ctrl === true ? event.ctrlKey : true;
+        const shiftMatches = shortcut.shift === true ? event.shiftKey : true;
+        const altMatches = shortcut.alt === true ? event.altKey : true;
+
+        // Handle meta/cmd key with cross-platform support
+        let metaMatches = true;
+        if (shortcut.meta === true) {
+          // On Mac: require Cmd key
+          // On Windows/Linux: accept Ctrl key as Cmd equivalent
+          const isMac = navigator.platform.includes('Mac');
+          metaMatches = isMac ? event.metaKey : event.ctrlKey;
+        }
+
+        // Ensure unwanted modifiers are not pressed (unless explicitly required)
+        const noExtraCtrl = shortcut.ctrl === true || shortcut.meta === true || !event.ctrlKey;
+        const noExtraShift = shortcut.shift === true || !event.shiftKey;
+        const noExtraAlt = shortcut.alt === true || !event.altKey;
+        const noExtraMeta = shortcut.meta === true || !event.metaKey;
+
+        if (
+          keyMatches &&
+          ctrlMatches &&
+          shiftMatches &&
+          altMatches &&
+          metaMatches &&
+          noExtraCtrl &&
+          noExtraShift &&
+          noExtraAlt &&
+          noExtraMeta
+        ) {
+          event.preventDefault();
+          shortcut.handler(event);
+          break;
+        }
+      }
+    };
+
+    window.addEventListener('keydown', handleKeyDown);
+
+    return () => {
+      window.removeEventListener('keydown', handleKeyDown);
+    };
+  }, [shortcuts]);
+}
+
+/**
+ * Hook to register a single keyboard shortcut (convenience wrapper)
+ */
+export function useKeyboardShortcut(
+  key: string,
+  handler: (event: KeyboardEvent) => void,
+  modifiers?: {
+    ctrl?: boolean;
+    shift?: boolean;
+    alt?: boolean;
+    meta?: boolean;
+  }
+) {
+  useKeyboard([
+    {
+      key,
+      ...modifiers,
+      handler,
+    },
+  ]);
+}