refactor(theme): remove light theme and enforce dark mode across all apps

tests/contracts/MockERC20.sol

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
+contract MockERC20 is ERC20 {
+    constructor(string memory name, string memory symbol, uint256 initialSupply) ERC20(name, symbol) {
+        _mint(msg.sender, initialSupply);
+    }
+}