feat(config): integrate etcd for service discovery and config management

- Add etcd-client dependency for distributed configuration storage
- Implement EtcdConfig with priority: etcd > environment variables > defaults
- Add ServiceRegistry for service registration with lease keep-alive
- Integrate etcd-based service discovery for appks gRPC connections
- Add service watcher for real-time service instance updates
- Migrate Redis configuration from single URL to cluster node list
- Update Dockerfile with default IMKS_HOST and IMKS_PORT environment variables
- Add etcd bootstrap configuration through environment variables
- Implement Redis cluster URL building with optional authentication

engine/session.rs

@@ -132,7 +132,10 @@ impl SessionStore {
         if let Some(m) = crate::telemetry::metrics::try_get() {
             m.engine_sessions_active.add(
                 1,
-                &[opentelemetry::KeyValue::new("transport", transport.as_str())],
+                &[opentelemetry::KeyValue::new(
+                    "transport",
+                    transport.as_str(),
+                )],
             );
         }
         rx