ADR-0042: Catalog entries stay in_development until signed artifacts are released

Status: Accepted (WP-70f). Applied in projects/bitnami-migration/candidates/{nginx,redis-valkey,postgresql} and the catalog README's legend.

Context

The plan expected the Bitnami migration catalog to mark nginx, Valkey and PostgreSQL as available once their projects existed. The catalog's own legend defines available as "released, signed CommonLayer artifacts exist". The three projects are built and tested in this repository, but nothing has been published to a CommonLayer registry, signed or attested.

Decision

• The three entries have status in_development, and the legend says what that means for them: images and charts exist in this repository and are built and tested, but there is nothing to pull from CommonLayer.
• An entry becomes available only with its first release, which first needs the base image released and its digest filled into the manifests (projects/base/README.md, "the one-time bootstrap order").
• The deep migration guides describe the real images and charts (value names from the charts' values.yaml), so users can try a migration with images they build themselves.

Consequences

• The catalog does not promise artifacts that do not exist. It deviates from plan 10 §7.
• Someone has to change the status at the first release; nothing does it automatically.