pg_vectorize self-host needs preload restart and embedding service URL

This applies to the pgvectorize SQL-extension deployment, not its separate HTTP-server mode. For an existing PostgreSQL instance, the extension guide lists vectorize and `pgcron in sharedpreloadlibraries and sets cron.database_name`. PostgreSQL must restart for the preload-library change to take effect.

If the extension calls a self-hosted vector-serve, set vectorize.embedding_service_url to an address reachable from the PostgreSQL server. The guide’s loopback example works only when the service shares the database host’s network context; a separate container or host needs the corresponding reachable service address. Check the Postgres logs after restart and confirm the extension can reach the configured service.