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/interfaces/draft-IERC7802.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.4.0) (interfaces/draft-IERC7802.sol)
+pragma solidity >=0.6.2;
+
+import {IERC165} from "./IERC165.sol";
+
+/// @title IERC7802
+/// @notice Defines the interface for crosschain ERC20 transfers.
+interface IERC7802 is IERC165 {
+    /// @notice Emitted when a crosschain transfer mints tokens.
+    /// @param to       Address of the account tokens are being minted for.
+    /// @param amount   Amount of tokens minted.
+    /// @param sender   Address of the caller (msg.sender) who invoked crosschainMint.
+    event CrosschainMint(address indexed to, uint256 amount, address indexed sender);
+
+    /// @notice Emitted when a crosschain transfer burns tokens.
+    /// @param from     Address of the account tokens are being burned from.
+    /// @param amount   Amount of tokens burned.
+    /// @param sender   Address of the caller (msg.sender) who invoked crosschainBurn.
+    event CrosschainBurn(address indexed from, uint256 amount, address indexed sender);
+
+    /// @notice Mint tokens through a crosschain transfer.
+    /// @param _to     Address to mint tokens to.
+    /// @param _amount Amount of tokens to mint.
+    function crosschainMint(address _to, uint256 _amount) external;
+
+    /// @notice Burn tokens through a crosschain transfer.
+    /// @param _from   Address to burn tokens from.
+    /// @param _amount Amount of tokens to burn.
+    function crosschainBurn(address _from, uint256 _amount) external;
+}