CVE-2026-52732 ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, one unauthenticated P2P peer can monopolize all 25 MAXINBOUNDCONCURRENCY slots in Zebra's inbound mempool download and verification pipeline. In zebrad/src/components/mempool/downloads.rs, the bounded queue was shared globally withou...