Fix 3 warnings: unused import, unused variable, dead code

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/crates/warzone-server/src/state.rs

@@ -1,6 +1,6 @@
 use std::collections::HashMap;
 use std::sync::Arc;
-use tokio::sync::{broadcast, Mutex, mpsc};
+use tokio::sync::{Mutex, mpsc};
 
 use crate::db::Database;
 
@@ -52,6 +52,7 @@ impl AppState {
     }
 
     /// Unregister a WS connection.
+    #[allow(dead_code)]
     pub async fn unregister_ws(&self, fingerprint: &str, sender: &WsSender) {
         let mut conns = self.connections.lock().await;
         if let Some(senders) = conns.get_mut(fingerprint) {