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/figletService.ts

@@ -0,0 +1,80 @@
+'use client';
+
+import figlet from 'figlet';
+import type { FigletOptions } from '@/types/figlet';
+import { loadFont } from './fontLoader';
+
+/**
+ * Convert text to ASCII art using figlet
+ */
+export async function textToAscii(
+  text: string,
+  fontName: string = 'Standard',
+  options: FigletOptions = {}
+): Promise<string> {
+  if (!text) {
+    return '';
+  }
+
+  try {
+    // Load the font
+    const fontData = await loadFont(fontName);
+
+    if (!fontData) {
+      throw new Error(`Font ${fontName} could not be loaded`);
+    }
+
+    // Parse and load the font into figlet
+    figlet.parseFont(fontName, fontData);
+
+    // Generate ASCII art
+    return new Promise((resolve, reject) => {
+      figlet.text(
+        text,
+        {
+          font: fontName,
+          horizontalLayout: options.horizontalLayout || 'default',
+          verticalLayout: options.verticalLayout || 'default',
+          width: options.width,
+          whitespaceBreak: options.whitespaceBreak ?? true,
+        },
+        (err, result) => {
+          if (err) {
+            reject(err);
+          } else {
+            resolve(result || '');
+          }
+        }
+      );
+    });
+  } catch (error) {
+    console.error('Error generating ASCII art:', error);
+    throw error;
+  }
+}
+
+/**
+ * Generate ASCII art synchronously (requires font to be pre-loaded)
+ */
+export function textToAsciiSync(
+  text: string,
+  fontName: string = 'Standard',
+  options: FigletOptions = {}
+): string {
+  if (!text) {
+    return '';
+  }
+
+  try {
+    return figlet.textSync(text, {
+      font: fontName as any,
+      horizontalLayout: options.horizontalLayout || 'default',
+      verticalLayout: options.verticalLayout || 'default',
+      width: options.width,
+      whitespaceBreak: options.whitespaceBreak ?? true,
+    });
+  } catch (error) {
+    console.error('Error generating ASCII art (sync):', error);
+    return '';
+  }
+}