Changed the default PostgreSQL version from 12 to 13 in both the setup script and the JSON configuration. Also removed a redundant password change warning from the JSON notes.
Simplifies the update process in ct/postgresus.sh by using a helper function for fetching and deploying releases, streamlining frontend and backend build steps, and improving status messages. Updates the logo URL in frontend/public/json/postgresus.json to use a CDN-hosted image.