Fix ESLint 9 configuration and resolve compatibility issues

- Configure ESLint 9 flat config with direct plugin imports
- Add TypeScript parser and plugins for proper code analysis
- Fix rushstack/eslint-patch compatibility issue
- Add global variables (React, console, process) for proper linting
- Resolve unused variable warning in middleware.ts
- Update rules: no-explicit-any as warning, support unused vars with underscore prefix

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

eslint.config.mjs

@@ -1,18 +1,72 @@
-import { defineConfig, globalIgnores } from "eslint/config";
-import nextVitals from "eslint-config-next/core-web-vitals";
-import nextTs from "eslint-config-next/typescript";
+import js from "@eslint/js";
+import nextPlugin from "@next/eslint-plugin-next";
+import tseslint from "@typescript-eslint/eslint-plugin";
+import tsparser from "@typescript-eslint/parser";
+import reactPlugin from "eslint-plugin-react";
+import reactHooksPlugin from "eslint-plugin-react-hooks";
 
-const eslintConfig = defineConfig([
-  ...nextVitals,
-  ...nextTs,
-  // Override default ignores of eslint-config-next.
-  globalIgnores([
-    // Default ignores of eslint-config-next:
-    ".next/**",
-    "out/**",
-    "build/**",
-    "next-env.d.ts",
-  ]),
-]);
+const eslintConfig = [
+  {
+    ignores: [
+      ".next/**",
+      "out/**",
+      "build/**",
+      "dist/**",
+      "node_modules/**",
+      "next-env.d.ts",
+    ],
+  },
+  js.configs.recommended,
+  {
+    files: ["**/*.{js,jsx,mjs}"],
+    plugins: {
+      "@next/next": nextPlugin,
+      "react": reactPlugin,
+      "react-hooks": reactHooksPlugin,
+    },
+    rules: {
+      ...nextPlugin.configs.recommended.rules,
+      ...nextPlugin.configs["core-web-vitals"].rules,
+    },
+  },
+  {
+    files: ["**/*.{ts,tsx}"],
+    languageOptions: {
+      parser: tsparser,
+      parserOptions: {
+        ecmaVersion: "latest",
+        sourceType: "module",
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+      globals: {
+        React: "readonly",
+        console: "readonly",
+        process: "readonly",
+        __dirname: "readonly",
+        __filename: "readonly",
+        Buffer: "readonly",
+      },
+    },
+    plugins: {
+      "@typescript-eslint": tseslint,
+      "@next/next": nextPlugin,
+      "react": reactPlugin,
+      "react-hooks": reactHooksPlugin,
+    },
+    rules: {
+      ...tseslint.configs.recommended.rules,
+      ...nextPlugin.configs.recommended.rules,
+      ...nextPlugin.configs["core-web-vitals"].rules,
+      "react/react-in-jsx-scope": "off",
+      "@typescript-eslint/no-explicit-any": "warn",
+      "@typescript-eslint/no-unused-vars": ["error", {
+        "argsIgnorePattern": "^_",
+        "varsIgnorePattern": "^_"
+      }],
+    },
+  },
+];
 
 export default eslintConfig;