images.py: extend AMD64_ONLY_IMAGES with the three impress (La Suite Docs)
images — impress-backend, impress-frontend, impress-y-provider. Always pull
the amd64 manifest + layers by digest unconditionally before the blob check;
the prior guard skipped the pull when the index blob was present but layers
were missing, causing the OCI import to fail on arm64 hosts.
secrets.py: add docs KV path (django-secret-key, collaboration-secret) to
_seed_openbao so a fresh sunbeam seed generates all required credentials for
the impress deployment.