feat: first version of the interface, integrate Tailwind CSS and update routing

- Add Tailwind CSS dependencies and configure Vite to use Tailwind
- Implement routing with React Router for Landing and Dashboard pages
- Remove unused App.css file and refactor App component to utilize new structure
- Update global styles in index.css to incorporate Tailwind's utility classes

frontend/vite.config.js

@@ -1,7 +1,8 @@
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
+import tailwindcss from '@tailwindcss/vite'
 
 // https://vite.dev/config/
 export default defineConfig({
-  plugins: [react()],
+  plugins: [react(), tailwindcss()],
 })