v0.47.0 — CDC, backup, PITR, prepared statements, cross-request HTTP sessions, FK final-write-set, metrics and audit log

What's new in v0.47.0

Server (mongreldb-server)

• Cross-request HTTP sessions for interactive transactions — keep a transaction open across multiple HTTP calls via session-bound TxnState.
• Prepared-statement REST API over HTTP sessions — prepare, execute, deallocate endpoints; bind values across requests.
• Metrics, audit log, and Arrow streaming — /metrics, /audit, Arrow JSON/streaming over /sql.
• Idempotent create-table — accept default_value as alias for default_expr in /kit/create_table.

Core (mongreldb-core)

• Foreign-key final-write-set enforcement — core FK final-write-set integrates referential integrity with the WAL group-commit path.
• CDC, backup, and PITR — change-data-capture stream + cold/offline backups + point-in-time restore with additional test coverage.

Tooling

• Cross-engine benchmark matrix refreshed (34 language clients documented).
• rustfmt applied across mongreldb-core and mongreldb-server.
• Code review pass: address Codex peer-review findings across the shipped features.

Stats since v0.46.2

• 954 tests passing, 1 ignored.
• cargo fmt --check, cargo clippy --workspace --all-targets --all-features -- -D warnings, and cargo test --workspace --all-features all green.