fix: eliminate all compiler warnings

- 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.

src/ip_tracker.rs

@@ -1,5 +1,7 @@
 // src/ip_tracker.rs
-// Модуль для отслеживания и ограничения уникальных IP-адресов пользователей
+// IP address tracking and limiting for users
+
+#![allow(dead_code)]
 
 use std::collections::{HashMap, HashSet};
 use std::net::IpAddr;