fix: fire-and-forget checks so slow monitors don't delay fast ones

apps/monitor/src/runner.rs

@@ -25,8 +25,8 @@ pub async fn fetch_and_run(
     let n = monitors.len();
     if n == 0 { return Ok(0); }
 
-    // Run all checks concurrently
-    let tasks: Vec<_> = monitors.into_iter().map(|monitor| {
+    // Spawn all checks — fire and forget, don't block the cycle
+    for monitor in monitors {
         let client = client.clone();
         let coordinator_url = coordinator_url.to_string();
         let token = token.to_string();
@@ -35,10 +35,9 @@ pub async fn fetch_and_run(
             if let Err(e) = post_result(&client, &coordinator_url, &token, result).await {
                 warn!("Failed to post result for {}: {e}", monitor.id);
             }
-        })
-    }).collect();
+        });
+    }
 
-    futures::future::join_all(tasks).await;
     Ok(n)
 }