fix(health/check): validate URL port before dialing in Stream check

Add port validation to return an unhealthy result with descriptive
message when URL has no port specified, preventing potential dialing
errors on zero port.

internal/health/check/stream.go

@@ -12,6 +12,14 @@ import (
 )
 
 func Stream(ctx context.Context, url *url.URL, timeout time.Duration) (types.HealthCheckResult, error) {
+	if port := url.Port(); port == "" || port == "0" {
+		return types.HealthCheckResult{
+			Latency: 0,
+			Healthy: false,
+			Detail:  "no port specified",
+		}, nil
+	}
+
 	dialer := net.Dialer{
 		Timeout:       timeout,
 		FallbackDelay: -1,