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/utils/Nonces.sol

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.0.0) (utils/Nonces.sol)
+pragma solidity ^0.8.20;
+
+/**
+ * @dev Provides tracking nonces for addresses. Nonces will only increment.
+ */
+abstract contract Nonces {
+    /**
+     * @dev The nonce used for an `account` is not the expected current nonce.
+     */
+    error InvalidAccountNonce(address account, uint256 currentNonce);
+
+    mapping(address account => uint256) private _nonces;
+
+    /**
+     * @dev Returns the next unused nonce for an address.
+     */
+    function nonces(address owner) public view virtual returns (uint256) {
+        return _nonces[owner];
+    }
+
+    /**
+     * @dev Consumes a nonce.
+     *
+     * Returns the current value and increments nonce.
+     */
+    function _useNonce(address owner) internal virtual returns (uint256) {
+        // For each account, the nonce has an initial value of 0, can only be incremented by one, and cannot be
+        // decremented or reset. This guarantees that the nonce never overflows.
+        unchecked {
+            // It is important to do x++ and not ++x here.
+            return _nonces[owner]++;
+        }
+    }
+
+    /**
+     * @dev Same as {_useNonce} but checking that `nonce` is the next valid for `owner`.
+     */
+    function _useCheckedNonce(address owner, uint256 nonce) internal virtual {
+        uint256 current = _useNonce(owner);
+        if (nonce != current) {
+            revert InvalidAccountNonce(owner, current);
+        }
+    }
+}