Updates dashboard UI and improves styling

Improves the dashboard's appearance and user experience by updating styles and layouts.

Changes include:
- Updates to color schemes and spacing for better readability and visual appeal.
- Implements a responsive layout for the header to adapt to different screen sizes.
- Refactors button styles for consistency and clarity.
- Adds a gradient background to the main dashboard page.
- Updates the NextAuth URL in the development environment.

tailwind.config.js

@@ -1,5 +1,5 @@
 /** @type {import('tailwindcss').Config} */
-export default {
+const config = {
   content: [
     "./pages/**/*.{js,ts,jsx,tsx,mdx}",
     "./components/**/*.{js,ts,jsx,tsx,mdx}",
@@ -10,3 +10,5 @@ export default {
   },
   plugins: [],
 };
+
+export default config;