feat: Add Todo page mockup and layout Wrapper components

Key Changes:
- Created Wrapper components (Fullscreen, Column, Container, ListedComponent) to standardize the application's overall layout.
- Refactored the structure of major components like App.tsx and PageContainer.tsx to use the new Wrapper components.
- Added a simple TodoBoard mockup page at the /todos route.
- Adjusted flexbox classes for the TodoBoard component to allow its width to resize flexibly based on screen size.

src/styles/index.css

@@ -1,6 +1,10 @@
 @import url('https://cdnjs.cloudflare.com/ajax/libs/pretendard/1.3.9/static/pretendard.min.css');
 @import 'tailwindcss';
 @import 'tw-animate-css';
+@plugin 'tailwind-scrollbar' {
+  nocompatible: true;
+  preferredstrategy: 'pseudoelements';
+}
 
 @custom-variant dark (&:is(.dark *));