refactor: move brother_node development artifact to dev/test-nodes subdirectory

Development Artifact Cleanup:
✅ BROTHER_NODE REORGANIZATION: Moved development test node to appropriate location
- dev/test-nodes/brother_node/: Moved from root directory for better organization
- Contains development configuration, test logs, and test chain data
- No impact on production systems - purely development/testing artifact

✅ DEVELOPMENT ARTIFACTS IDENTIFIED:
- Chain ID: aitbc-brother-chain (test/development chain)
- Ports: 8010 (P2P) and 8011 (RPC) - different from production
- Environment: .env file with test configuration
- Logs: rpc.log and node.log from development testing session (March 15, 2026)

✅ ROOT DIRECTORY CLEANUP: Removed development clutter from production directory
- brother_node/ moved to dev/test-nodes/brother_node/
- Root directory now contains only production-ready components
- Development artifacts properly organized in dev/ subdirectory

DIRECTORY STRUCTURE IMPROVEMENT:
📁 dev/test-nodes/: Development and testing node configurations
🏗️ Root Directory: Clean production structure with only essential components
🧪 Development Isolation: Test environments separated from production

BENEFITS:
✅ Clean Production Directory: No development artifacts in root
✅ Better Organization: Development nodes grouped in dev/ subdirectory
✅ Clear Separation: Production vs development environments clearly distinguished
✅ Maintainability: Easier to identify and manage development components

RESULT: Successfully moved brother_node development artifact to dev/test-nodes/ subdirectory, cleaning up the root directory while preserving development testing environment for future use.

dev/env/node_modules/@openzeppelin/contracts/access/Ownable2Step.sol

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.1.0) (access/Ownable2Step.sol)
+
+pragma solidity ^0.8.20;
+
+import {Ownable} from "./Ownable.sol";
+
+/**
+ * @dev Contract module which provides access control mechanism, where
+ * there is an account (an owner) that can be granted exclusive access to
+ * specific functions.
+ *
+ * This extension of the {Ownable} contract includes a two-step mechanism to transfer
+ * ownership, where the new owner must call {acceptOwnership} in order to replace the
+ * old one. This can help prevent common mistakes, such as transfers of ownership to
+ * incorrect accounts, or to contracts that are unable to interact with the
+ * permission system.
+ *
+ * The initial owner is specified at deployment time in the constructor for `Ownable`. This
+ * can later be changed with {transferOwnership} and {acceptOwnership}.
+ *
+ * This module is used through inheritance. It will make available all functions
+ * from parent (Ownable).
+ */
+abstract contract Ownable2Step is Ownable {
+    address private _pendingOwner;
+
+    event OwnershipTransferStarted(address indexed previousOwner, address indexed newOwner);
+
+    /**
+     * @dev Returns the address of the pending owner.
+     */
+    function pendingOwner() public view virtual returns (address) {
+        return _pendingOwner;
+    }
+
+    /**
+     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
+     * Can only be called by the current owner.
+     *
+     * Setting `newOwner` to the zero address is allowed; this can be used to cancel an initiated ownership transfer.
+     */
+    function transferOwnership(address newOwner) public virtual override onlyOwner {
+        _pendingOwner = newOwner;
+        emit OwnershipTransferStarted(owner(), newOwner);
+    }
+
+    /**
+     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
+     * Internal function without access restriction.
+     */
+    function _transferOwnership(address newOwner) internal virtual override {
+        delete _pendingOwner;
+        super._transferOwnership(newOwner);
+    }
+
+    /**
+     * @dev The new owner accepts the ownership transfer.
+     */
+    function acceptOwnership() public virtual {
+        address sender = _msgSender();
+        if (pendingOwner() != sender) {
+            revert OwnableUnauthorizedAccount(sender);
+        }
+        _transferOwnership(sender);
+    }
+}