Implement multi-host autoconnect with consolidated host configuration

- Add DEFAULT_HOSTS constant in config.rs for centralized host management
- Update ZMQ endpoint generation to connect to all configured hosts
- Implement graceful connection handling for unreachable endpoints
- Dashboard now auto-discovers and connects to available agents on cmbox, labbox, simonbox, steambox, srv01

dashboard/src/main.rs

@@ -249,12 +249,25 @@ fn metrics_blocking_loop(
         .set_rcvtimeo(1_000)
         .context("failed to configure ZMQ receive timeout")?;
 
+    let mut connected_endpoints = 0;
     for endpoint in context.endpoints() {
-        debug!(%endpoint, "connecting to ZMQ endpoint");
-        socket
-            .connect(endpoint)
-            .with_context(|| format!("failed to connect to {endpoint}"))?;
+        debug!(%endpoint, "attempting to connect to ZMQ endpoint");
+        match socket.connect(endpoint) {
+            Ok(()) => {
+                debug!(%endpoint, "successfully connected to ZMQ endpoint");
+                connected_endpoints += 1;
+            }
+            Err(error) => {
+                warn!(%endpoint, %error, "failed to connect to ZMQ endpoint, continuing with others");
+            }
+        }
     }
+    
+    if connected_endpoints == 0 {
+        return Err(anyhow!("failed to connect to any ZMQ endpoints"));
+    }
+    
+    debug!("connected to {}/{} ZMQ endpoints", connected_endpoints, context.endpoints().len());
 
     if let Some(prefix) = context.subscription() {
         socket