refactor: rm callback verifier dispatcher

foundry/interfaces/ICallback.sol

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.26;
+
+interface ICallback {
+    error UnauthorizedCaller(string exchange, address sender);
+
+    function handleCallback(
+        bytes calldata data
+    ) external returns (bytes memory result);
+}