- Remove unused imports across multiple modules
- Add #![allow(dead_code)] for public API items preserved for future use
- Add #![allow(deprecated)] for rand::Rng::gen_range usage
- Add #![allow(unused_assignments)] in main.rs
- Add #![allow(unreachable_code)] in network/stun.rs
- Prefix unused variables with underscore (_ip_tracker, _prefer_ipv6)
- Fix unused_must_use warning in tls_front/cache.rs
This ensures clean compilation without warnings while preserving
public API items that may be used in the future.
When IPv6 is unavailable on the host, treat NetworkUnreachable at
connect() as Ok(None) instead of propagating an error, so the dual
STUN probe succeeds with just the IPv4 result and no spurious WARN.
