Previously translate_log_for_active_languages and
translate_summary_for_active_languages added every successful
translation to the session and called session.commit() once at the
end. A single bad row (DB error, constraint violation, encoding
mismatch) rolled back the whole batch — losing all the languages that
had succeeded.
Wrap each row in session.begin_nested() so a per-row failure only
loses that one row. Track succeeded/failed counts and log them at the
end — escalating to error if zero succeeded out of N attempted, so
total failure surfaces in monitoring instead of just N warning lines.