feat(auth): implement role-based access control and user management features

frontend/middleware.ts

@@ -17,6 +17,14 @@ export default auth((req) => {
     return NextResponse.redirect(loginUrl);
   }
 
+  // Admin-sidor kräver admin-roll
+  if (pathname.startsWith('/admin')) {
+    const role = (req.auth.user as any)?.role;
+    if (role !== 'admin') {
+      return NextResponse.redirect(new URL('/', req.url));
+    }
+  }
+
   return NextResponse.next();
 });