fix: add connect_timeout to reqwest client to prevent indefinite TCP SYN hangs

apps/monitor/src/main.rs

@@ -31,6 +31,7 @@ async fn main() -> Result<()> {
 
     let client = reqwest::Client::builder()
         .user_agent("PingQL-Monitor/0.1")
+        .connect_timeout(std::time::Duration::from_secs(10))
         .build()?;
 
     let in_flight: Arc<Mutex<HashSet<String>>> = Arc::new(Mutex::new(HashSet::new()));