feat: add authentication support and user model

- Updated `env.example` to include NextAuth configuration for authentication.
- Added `next-auth` dependency to manage user sessions.
- Introduced `User` model in Prisma schema with fields for user details and password hashing.
- Integrated `AuthProvider` in layout for session management across the app.
- Enhanced `Header` component with `AuthButton` for user authentication controls.

src/components/AuthProvider.tsx

@@ -0,0 +1,7 @@
+'use client'
+
+import { SessionProvider } from "next-auth/react"
+
+export function AuthProvider({ children }: { children: React.ReactNode }) {
+  return <SessionProvider>{children}</SessionProvider>
+}