fix(auth): correct local cookie security configuration

validation-suite/frontend/atlas/lib/auth.ts

@@ -0,0 +1,13 @@
+export const AUTH_COOKIE_NAME = process.env.AUTH_COOKIE_NAME ?? "atlas_access_token";
+export const AUTH_COOKIE_SECURE = process.env.AUTH_COOKIE_SECURE?.trim().toLowerCase() === "true";
+export const AUTH_COOKIE_SAMESITE = (process.env.AUTH_COOKIE_SAMESITE ?? "lax").trim().toLowerCase();
+
+export function buildAuthCookieOptions(maxAge: number) {
+  return {
+    httpOnly: true as const,
+    secure: AUTH_COOKIE_SECURE,
+    sameSite: AUTH_COOKIE_SAMESITE as "lax" | "strict" | "none",
+    path: "/" as const,
+    maxAge
+  };
+}