Gateway: fallback routes per host, for the laptop's VPN address

gateway/test/notify.test.ts

@@ -95,6 +95,7 @@ describe("Notifier", () => {
       id: "host-1",
       label: "Mac mini",
       url: "https://t3mac.gbrown.org",
+      alt_urls: null,
       environment_id: "host-1",
       token: "t",
       token_expires_at: new Date(Date.now() + 3 * 24 * 60 * 60_000).toISOString(),