feat: Refactor layout and add toast notifications

This commit introduces a major structural refactoring by creating a shared application layout and integrates a toast notification system.

Key changes:
- A new `layout.tsx` file now contains the common Header and Footer components, ensuring a consistent structure across all pages.
- The main `page.tsx` has been simplified to only contain its specific content, with layout elements removed.
- The `react-toastify` library has been added to provide user feedback through toast notifications.
- Custom CSS styles have been applied to the toast notifications for a branded look and feel, including different gradient backgrounds for success, error, warning, and info states.
- The `.gitignore` file was updated to explicitly track the `.env` file, likely for an example configuration.

.gitignore

@@ -39,3 +39,4 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+!.env