refactor(app-host): conditionally spread authToken to avoid undefined

Address code review feedback: only include authToken in TursoDriver
config when the env var is actually set.

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>
Agent-Logs-Url: https://github.com/objectstack-ai/spec/sessions/1190de98-61cc-419b-b502-b9728e8e3db8

Author: Copilot

examples/app-host/objectstack.config.ts

@@ -38,7 +38,7 @@ export default defineStack({
     // Register Default Driver (Turso — remote mode on Vercel, in-memory for local dev)
     new DriverPlugin(new TursoDriver({
       url: process.env.TURSO_DATABASE_URL ?? ':memory:',
-      authToken: process.env.TURSO_AUTH_TOKEN,
+      ...(process.env.TURSO_AUTH_TOKEN && { authToken: process.env.TURSO_AUTH_TOKEN }),
     })),
     // Authentication — required for production (Vercel) deployments
     authPlugin,
@@ -106,7 +106,7 @@ export const PreviewHostExample = defineStack({
     new ObjectQLPlugin(),
     new DriverPlugin(new TursoDriver({
       url: process.env.TURSO_DATABASE_URL ?? ':memory:',
-      authToken: process.env.TURSO_AUTH_TOKEN,
+      ...(process.env.TURSO_AUTH_TOKEN && { authToken: process.env.TURSO_AUTH_TOKEN }),
     })),
     authPlugin,
     new AppPlugin(CrmApp),