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/AuthButton.tsx

@@ -0,0 +1,56 @@
+'use client'
+
+import { useSession, signOut } from 'next-auth/react'
+import { useRouter } from 'next/navigation'
+import { Button } from '@/components/ui/Button'
+
+export function AuthButton() {
+  const { data: session, status } = useSession()
+  const router = useRouter()
+
+  if (status === 'loading') {
+    return (
+      <div className="text-[var(--muted-foreground)] text-sm">
+        Chargement...
+      </div>
+    )
+  }
+
+  if (!session) {
+    return (
+      <Button
+        onClick={() => router.push('/login')}
+        size="sm"
+      >
+        Se connecter
+      </Button>
+    )
+  }
+
+  return (
+    <div className="flex items-center gap-1">
+      <Button
+        onClick={() => router.push('/profile')}
+        variant="ghost"
+        size="sm"
+        className="p-1 h-auto"
+        title={`Profil - ${session.user?.email}`}
+      >
+        <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M16 7a4 4 0 11-8 0 4 4 0 018 0zM12 14a7 7 0 00-7 7h14a7 7 0 00-7-7z" />
+        </svg>
+      </Button>
+      <Button
+        onClick={() => signOut({ callbackUrl: '/login' })}
+        variant="ghost"
+        size="sm"
+        className="p-1 h-auto"
+        title="Déconnexion"
+      >
+        <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M17 16l4-4m0 0l-4-4m4 4H7m6 4v1a3 3 0 01-3 3H6a3 3 0 01-3-3V7a3 3 0 013-3h4a3 3 0 013 3v1" />
+        </svg>
+      </Button>
+    </div>
+  )
+}