#919 Native psycopg C implementation; drop psycopg2-binary and psycopg[binary]

EARS SPEC: - The images shall install psycopg with the C implementation built against libpq and no binary wheel. - The health endpoint shall report psycopg implementation and fail readiness if it is not 'c'. Parent epic: #913. Synthesis (technical problems / solution domains / alternatives) recorded as a comment when started.