Add a docker build step.

frontend/react-router.config.ts

@@ -4,4 +4,7 @@ export default {
   // Config options...
   // Server-side render by default, to enable SPA mode set this to `false`
   ssr: true,
+  serverBuildDirectory: "build/server",
+  serverModuleFormat: "esm",
+  serverMiddleware: "./middleware.js",
 } satisfies Config;