Update ESLint config to use FlatCompat and expand ignores

Switched to using FlatCompat for ESLint configuration and extended the ignore list to include 'next-env.d.ts', 'postcss.config.js', and 'prettier.config.js'. This improves compatibility and prevents linting of config and environment files.

eslint.config.js

@@ -1,9 +1,13 @@
-import nextCoreWebVitals from "eslint-config-next/core-web-vitals";
+import { FlatCompat } from "@eslint/eslintrc";
 import tseslint from "typescript-eslint";
 
+const compat = new FlatCompat({
+  baseDirectory: import.meta.dirname,
+});
+
 export default tseslint.config(
   {
-    ignores: [".next"],
+    ignores: [".next", "next-env.d.ts", "postcss.config.js", "prettier.config.js"],
   },
   ...compat.extends("next/core-web-vitals"),
   {