Add health command for hub and align agent health command

beszel/internal/agent/health.go

@@ -6,14 +6,13 @@ import (
 )
 
 // Health checks if the agent's server is running by attempting to connect to it.
-// It returns 0 if the server is running, 1 otherwise (as in exit codes).
 //
 // If an error occurs when attempting to connect to the server, it returns the error.
-func Health(addr string, network string) (int, error) {
+func Health(addr string, network string) error {
 	conn, err := net.DialTimeout(network, addr, 4*time.Second)
 	if err != nil {
-		return 1, err
+		return err
 	}
 	conn.Close()
-	return 0, nil
+	return nil
 }