Bitnami retired the versioned tags under docker.io/bitnami and republished
the archived builds under docker.io/bitnamilegacy, so every install and
upgrade of the chart with the bundled database fails to pull
docker.io/bitnami/postgresql:16.2.0-debian-12-r6. Repoint the subchart
images at the bitnamilegacy copies of the exact builds those subchart
versions shipped with, so the on-disk data directory layout is unchanged
for existing installs.
Pin the subchart dependency ranges to the versions already in Chart.lock.
The current bitnami postgresql chart defaults to `tag: latest`, which is
PostgreSQL 18 today, so an open-ended range turns a dependency refresh
into a major-version jump on an existing volume.
Refuse to render when postgresql.image.tag is empty or `latest` while the
bundled database is deployed. Starting a different PostgreSQL major
against an existing data directory leaves the server unable to boot with
no in-place way back, which is how the reported install lost its data.
Resolves LIT-4708
