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

tsconfig.json

@@ -17,6 +17,7 @@
     "isolatedModules": true,
     "jsx": "react-jsx",
     "incremental": true,
+    "baseUrl": ".",
     "plugins": [
       {
         "name": "next"