[#893] Add finalize script and MerkleClaim contract

contracts/MerkleClaim.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+/**
+ * @title PLOTAirdrop
+ * @notice Merkle-tree based airdrop claim contract for PLOT tokens.
+ * @dev Standard OpenZeppelin MerkleProof-based contract.
+ *      Deploy with the PLOT token address and Merkle root from the finalize script.
+ */
+contract PLOTAirdrop {
+    IERC20 public immutable PLOT;
+    bytes32 public immutable merkleRoot;
+    mapping(address => bool) public claimed;
+
+    event Claimed(address indexed account, uint256 amount);
+
+    constructor(address _plot, bytes32 _merkleRoot) {
+        PLOT = IERC20(_plot);
+        merkleRoot = _merkleRoot;
+    }
+
+    function claim(uint256 amount, bytes32[] calldata proof) external {
+        require(!claimed[msg.sender], "Already claimed");
+
+        bytes32 leaf = keccak256(bytes.concat(keccak256(abi.encode(msg.sender, amount))));
+        require(MerkleProof.verify(proof, merkleRoot, leaf), "Invalid proof");
+
+        claimed[msg.sender] = true;
+        require(PLOT.transfer(msg.sender, amount), "Transfer failed");
+
+        emit Claimed(msg.sender, amount);
+    }
+}