build: Update ESLint to v9 (#16639)

packages/@n8n/config/eslint.config.mjs

@@ -0,0 +1,22 @@
+import { defineConfig } from 'eslint/config';
+import { nodeConfig } from '@n8n/eslint-config/node';
+
+export default defineConfig(
+	nodeConfig,
+	{
+		rules: {
+			'unicorn/filename-case': ['error', { case: 'kebabCase' }],
+
+			// TODO: Remove this
+			'@typescript-eslint/naming-convention': 'warn',
+			'@typescript-eslint/no-unsafe-call': 'warn',
+			'@typescript-eslint/no-unsafe-function-type': 'warn',
+		},
+	},
+	{
+		files: ['**/*.config.ts'],
+		rules: {
+			'n8n-local-rules/no-untyped-config-class-field': 'error',
+		},
+	},
+);