This commit replaces the basic placeholder with a full-featured demo page showcasing Tailwind CSS v4 capabilities.
- Implements a modern, responsive landing page layout in `TailwindcssDemo.vue`.
- Defines a custom primary color palette and a float animation using the new `@theme` at-rule in `main.css`.
- Adds a custom `.text-gradient` utility class.
- Updates the router to nest the demo page, improving scalability for future routes.
This commit integrates Tailwind CSS into the project for utility-first styling.
- Adds `tailwindcss` and `@tailwindcss/vite` as dependencies.
- Configures the Vite build process to use the Tailwind plugin.
- Sets up the main CSS entry point to import Tailwind styles.
- Adds a new route and a `TailwindcssDemo` component to verify the setup.
