Replace rand::random() with rand::rngs::OsRng for cryptographic nonce
and salt generation in encryption.rs. rand::random() uses thread-local
RNG which may not be a CSPRNG on all platforms; OsRng reads from the
OS entropy source, preventing catastrophic IV reuse under AES-GCM.
Drift item #1 (security-critical).
glm-5.2
f43246b978