fix: resolve performance issues causing UI lag

eslint.config.js

@@ -0,0 +1,61 @@
+// Flat ESLint config for ESLint v9+, migrated from .eslintrc.json
+import preactConfig from "eslint-config-preact";
+import tsPlugin from "@typescript-eslint/eslint-plugin";
+import tsParser from "@typescript-eslint/parser";
+import reactPlugin from "eslint-plugin-react";
+import prettierPlugin from "eslint-plugin-prettier";
+import jestPlugin from "eslint-plugin-jest";
+
+/** @type {import("eslint").Linter.FlatConfig[]} */
+export default [
+  {
+    ignores: ["build", ".vscode"],
+  },
+  {
+    files: ["src/**/*.{ts,tsx,js,jsx}", "scripts/**/*.{ts,js}"],
+    languageOptions: {
+      ecmaVersion: "latest",
+      sourceType: "module",
+      parser: tsParser,
+      globals: {
+        // Browser + ES2021 env equivalent
+        ...preactConfig.languageOptions?.globals,
+      },
+    },
+    plugins: {
+      "@typescript-eslint": tsPlugin,
+      react: reactPlugin,
+      prettier: prettierPlugin,
+      jest: jestPlugin,
+    },
+    rules: {
+      // Start from preact + recommended + TS recommended
+      ...(preactConfig.rules || {}),
+      ...tsPlugin.configs.recommended.rules,
+
+      // Project-specific rules from .eslintrc.json
+      "prettier/prettier": "error",
+      "react-hooks/exhaustive-deps": "off",
+      "@typescript-eslint/ban-ts-comment": "off",
+      "@typescript-eslint/no-explicit-any": "off",
+      "@typescript-eslint/no-non-null-assertion": "off",
+      "jest/expect-expect": "off",
+
+      // Globally ignore unused `h` (JSX pragma for Preact)
+      "@typescript-eslint/no-unused-vars": [
+        "error",
+        {
+          argsIgnorePattern: "^_",
+          varsIgnorePattern: "^h$",
+        },
+      ],
+    },
+    settings: {
+      react: {
+        pragma: "h",
+        version: "detect",
+      },
+    },
+  },
+];
+