feat: change default bind address to :: for dual‑stack support

The socket bound to :: accepts both IPv6 and IPv4 (mapped) connections,
so this change enables IPv6 connectivity in addition to the existing
IPv4 behaviour.

src/modules/settings/cli.rs

@@ -50,7 +50,7 @@ pub struct Settings {
     #[clap(
         long,
         env,
-        default_value = "0.0.0.0",
+        default_value = "::",
         help = "The IP address that the node binds to, in IPv4 or IPv6 format (e.g., 192.168.1.1 or ::1). Required in cluster mode.",
         value_parser = ValueParser::new(|s: &str| {
             // Ensure the input is a valid IPv4 or IPv6 address