durch
53c1689011
Add outer AEAD encryption + Ack message type for LP protocol
- Add OuterAeadKey derived from PSK via Blake3 KDF for packet encryption
- Add LpMessage::Ack (0x0008) for ClientHello acknowledgment
- Gateway sends Ack after processing ClientHello (packet-per-connection)
- Update codec with AEAD encrypt/decrypt using ChaCha20-Poly1305
- Header remains cleartext (AAD), payload encrypted after PSK derivation
- Add parse_lp_header_only() for routing before session lookup
- Update session to expose outer_aead_key() getter
- Various LP protocol improvements and test coverage
Closes: nym-f4v1, nym-n9dr