#744 Bootstrap only registers pre-installed apps, not example apps

The register_apps internal tool only scans enterprise/apps/pre_installed/ (8 apps). The 9 example apps in enterprise/apps/examples/ are never registered during bootstrap. This means after a clean deploy, those apps are missing from the marketplace and can't be installed for tenants. Fixed by adding EXAMPLE_APPS_DIR scan to register_apps and updating preinstalled_apps.yaml.