Fix Deadlock-Prone Mutex Usage in Message Handler

[devfire]

🚨 CRITICAL SAFETY VIOLATION

Location: message_handler.rs:80-81

Problem

let mut receiver = self.message_receiver.lock().await;
// ... infinite loop while holding lock

Issues

• Holding a mutex across an infinite loop
• Any async operation while locked will deadlock
• No timeout mechanism

Suggested Fix

// Use timeout for lock acquisition
let mut receiver = match tokio::time::timeout(
    Duration::from_millis(100),
    self.message_receiver.lock()
).await {
    Ok(lock) => lock,
    Err(_) => {
        warn!("Failed to acquire lock within timeout");
        continue;
    }
};

Priority: Critical - Deadlocks can freeze the entire system and require restart.