feat: adding kvbm-engine (#6773)

Signed-off-by: Ryan Olson <rolson@nvidia.com>

lib/kvbm-engine/src/object/s3/mod.rs

+// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//! S3-compatible object storage implementations.
+//!
+//! This module contains all S3-specific implementations:
+//! - [`S3ObjectBlockClient`] - Implements [`super::ObjectBlockOps`] for S3/MinIO
+//! - [`S3LockManager`] - Implements [`super::ObjectLockManager`] for distributed locking
+//!
+//! All types in this module are feature-gated behind `s3`. Consumers should use
+//! the factory functions in the parent [`object`](super) module to create trait
+//! objects without needing to depend on the `s3` feature.
+
+mod client;
+mod lock;
+
+pub use client::{S3Config, S3ObjectBlockClient};
+pub use lock::S3LockManager;