fix(auth): correct local cookie security configuration

validation-suite/frontend/atlas/app/api/logout/route.ts

@@ -0,0 +1,13 @@
+import { cookies } from "next/headers";
+import { NextResponse } from "next/server";
+import { AUTH_COOKIE_NAME, buildAuthCookieOptions } from "@/lib/auth";
+
+export async function POST() {
+  const cookieStore = await cookies();
+  cookieStore.set({
+    name: AUTH_COOKIE_NAME,
+    value: "",
+    ...buildAuthCookieOptions(0)
+  });
+  return NextResponse.json({ status: "ok" });
+}