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/proxy/beacon/UpgradeableBeacon.sol

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.0.0) (proxy/beacon/UpgradeableBeacon.sol)
+
+pragma solidity ^0.8.20;
+
+import {IBeacon} from "./IBeacon.sol";
+import {Ownable} from "../../access/Ownable.sol";
+
+/**
+ * @dev This contract is used in conjunction with one or more instances of {BeaconProxy} to determine their
+ * implementation contract, which is where they will delegate all function calls.
+ *
+ * An owner is able to change the implementation the beacon points to, thus upgrading the proxies that use this beacon.
+ */
+contract UpgradeableBeacon is IBeacon, Ownable {
+    address private _implementation;
+
+    /**
+     * @dev The `implementation` of the beacon is invalid.
+     */
+    error BeaconInvalidImplementation(address implementation);
+
+    /**
+     * @dev Emitted when the implementation returned by the beacon is changed.
+     */
+    event Upgraded(address indexed implementation);
+
+    /**
+     * @dev Sets the address of the initial implementation, and the initial owner who can upgrade the beacon.
+     */
+    constructor(address implementation_, address initialOwner) Ownable(initialOwner) {
+        _setImplementation(implementation_);
+    }
+
+    /**
+     * @dev Returns the current implementation address.
+     */
+    function implementation() public view virtual returns (address) {
+        return _implementation;
+    }
+
+    /**
+     * @dev Upgrades the beacon to a new implementation.
+     *
+     * Emits an {Upgraded} event.
+     *
+     * Requirements:
+     *
+     * - msg.sender must be the owner of the contract.
+     * - `newImplementation` must be a contract.
+     */
+    function upgradeTo(address newImplementation) public virtual onlyOwner {
+        _setImplementation(newImplementation);
+    }
+
+    /**
+     * @dev Sets the implementation contract address for this beacon
+     *
+     * Requirements:
+     *
+     * - `newImplementation` must be a contract.
+     */
+    function _setImplementation(address newImplementation) private {
+        if (newImplementation.code.length == 0) {
+            revert BeaconInvalidImplementation(newImplementation);
+        }
+        _implementation = newImplementation;
+        emit Upgraded(newImplementation);
+    }
+}