The host-side docker-compose mounts secrets/ and data/ read-only at
runtime, but the build context still slurped them in. Add secrets/,
data/, and general SSH key patterns (*.pem, *.key, id_rsa*,
id_ed25519*, known_hosts, .ssh/) so private material can never be
baked into the image even by accident.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
