Append entries and produce proofs

confium transparency append --artifact-hash "sha256:abc123..."
confium transparency prove --seq 0 --out proof.json

• The log is a database file (--db, default ./transparency.db); append-only by construction — treat any truncation as a security incident.
• Every append prints the new signed tree head; publish it wherever your witnesses look.
• Proofs are standalone JSON: entry, index, audit path, and head.