Ed25519 Precompile

A native Solana program (address: Ed25519SigVerify111111111111111111111111111) that enables batch verification of Ed25519 signatures within on-chain program logic. Unlike the runtime's built-in transaction signature verification, this precompile allows programs to verify arbitrary Ed25519 signatures over arbitrary data, useful for off-chain message verification, oracle attestations, and multi-party protocols. Multiple signatures can be verified in a single instruction.