GHSA-c8w6-x74f-vmg3: zebrad vulnerable to full node denial of service via crafted Sapling receiver in z_listunifiedreceivers

The z_listunifiedreceivers RPC handler panics when processing a structurally valid Unified Address whose Sapling receiver carries 43 bytes that fail cryptographic validation (sapling_crypto::PaymentAddress::from_bytes returns None for non-subgroup Jubjub points). The handler calls .expect("using data already decoded as valid") on the fallible result. Because Zebra’s release profile sets panic = "abort", the panic terminates the entire node process, not just the RPC task.