Fix TopstepX login loop on bundled builds: signalr's dynamic require

@microsoft/signalr does an unconditional require('ws')/require('eventsource')
when constructing a connection; bundled (turbopack) builds throw 'dynamic
usage of require is not supported', which the login chain mislabelled as a
login failure and retried every 60s. Externalize the package and never let
hub setup fail the login — REST polling covers everything the hub does.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

next.config.ts

@@ -1,7 +1,10 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  serverExternalPackages: ['better-sqlite3'],
+  // @microsoft/signalr does dynamic require('ws')/require('eventsource') for
+  // its Node transports — bundling it (turbopack production builds) throws
+  // "dynamic usage of require is not supported" the moment a hub is built.
+  serverExternalPackages: ['better-sqlite3', '@microsoft/signalr'],
 };
 
 export default nextConfig;