deps: update eslint to v9

frontend/eslint.config.mjs

@@ -0,0 +1,74 @@
+import { defineConfig } from "eslint/config";
+import typescriptEslint from "@typescript-eslint/eslint-plugin";
+import testingLibrary from "eslint-plugin-testing-library";
+import jest from "eslint-plugin-jest";
+import prettier from "eslint-plugin-prettier";
+import globals from "globals";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import js from "@eslint/js";
+import { FlatCompat } from "@eslint/eslintrc";
+import prettierConfig from "./.prettierrc.json" with {type: "json"}
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const compat = new FlatCompat({
+    baseDirectory: __dirname,
+    recommendedConfig: js.configs.recommended,
+    allConfig: js.configs.all
+});
+
+export default defineConfig([{
+    extends: compat.extends(
+        "next/core-web-vitals",
+        "eslint:recommended",
+        "plugin:@typescript-eslint/eslint-recommended",
+        "plugin:@typescript-eslint/recommended",
+        "plugin:@typescript-eslint/recommended-requiring-type-checking",
+        "prettier",
+    ),
+
+    plugins: {
+        "@typescript-eslint": typescriptEslint,
+        "testing-library": testingLibrary,
+        jest,
+        prettier,
+    },
+
+    languageOptions: {
+        globals: {
+            ...globals.jest,
+            ...jest.environments.globals.globals,
+        },
+
+        ecmaVersion: 5,
+        sourceType: "script",
+
+        parserOptions: {
+            tsconfigRootDir: ".",
+            project: ["./tsconfig.json"],
+        },
+    },
+
+    rules: {
+        "prettier/prettier": ["error", prettierConfig],
+
+        "no-use-before-define": "off",
+        "no-debugger": "warn",
+        "default-param-last": "off",
+
+        "@typescript-eslint/consistent-type-imports": ["error", {
+            prefer: "type-imports",
+            disallowTypeAnnotations: false,
+        }],
+
+        "jest/no-disabled-tests": "warn",
+        "jest/no-focused-tests": "error",
+        "jest/no-identical-title": "error",
+        "jest/prefer-to-have-length": "warn",
+        "jest/valid-expect": "error",
+    },
+}, {
+    files: ["**/__tests__/**/*.[jt]s?(x)", "**/?(*.)+(spec|test).[jt]s?(x)"],
+    extends: compat.extends("plugin:testing-library/react"),
+}]);