The backup container creates /backup/wal as root, but the postgres
archive_command runs as UID 999 and can't write to it.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Weekly full backups via pg_basebackup and continuous WAL archiving
for point-in-time recovery, running as Docker Compose services.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>