feat(bootstrap): fall back to built-in placeholder when marketplace unpublished

Adds published: boolean to the bootstrap wire contract. ConfigService
swaps to a new DEFAULT_BOOTSTRAP constant (all feature flags on, generic
branding/theme/pages) whenever the backend reports published: false, so
an unpublished marketplace renders a working demo instead of a blank or
broken page. Missing published field stays backward compatible (treated
as true). Documents the brand bootstrap wire shape for backend/ops use.

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

src/app/shared/models/config/index.ts

@@ -3,6 +3,7 @@ export * from './bootstrap-config.model';
 export * from './branding.model';
 export * from './catalog-config.model';
 export * from './company.model';
+export * from './default-bootstrap.const';
 export * from './feature-flags.model';
 export * from './features-config.model';
 export * from './footer-config.model';