AlphaRNG Adds RSA-4096 Support

AlphaRNG now supports RSA-4096 for secure session key exchange, joining RSA-3072, RSA-2048, and RSA-1024. Each AlphaRNG V1.2 device also ships with a unique per-device RSA-4096 public key.

This arrives as NIST moves to retire smaller RSA keys: under NIST IR 8547, 2048-bit RSA is deprecated by 2030, while RSA-4096 avoids that earlier date. All classical RSA, including 4096-bit, is disallowed by 2035 as part of the broader transition to post-quantum-safe cryptography, but RSA-4096 buys meaningfully more runway than RSA-2048 in the meantime.

Enable it with -p RSA4096 on the command line, RsaKeySize::rsa4096 in the C++ API, or rsa_4096_key in the C wrapper.