Switch ESLint config to eslint-config-next/core-web-vitals

Replaces @eslint/eslintrc and FlatCompat with eslint-config-next/core-web-vitals for ESLint configuration. Updates linting scripts in package.json to use eslint directly instead of next lint. Removes @eslint/eslintrc from devDependencies.

eslint.config.js

@@ -1,10 +1,6 @@
-import { FlatCompat } from "@eslint/eslintrc";
+import nextCoreWebVitals from "eslint-config-next/core-web-vitals";
 import tseslint from "typescript-eslint";
 
-const compat = new FlatCompat({
-  baseDirectory: import.meta.dirname,
-});
-
 export default tseslint.config(
   {
     ignores: [".next"],