Bump eslint from 8.57.0 to 9.0.0 in /src/backend (#6979)

* Bump eslint from 8.57.0 to 9.0.0 in /src/backend

Bumps [eslint](https://github.com/eslint/eslint) from 8.57.0 to 9.0.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/main/CHANGELOG.md)
- [Commits](https://github.com/eslint/eslint/compare/v8.57.0...v9.0.0)

---
updated-dependencies:
- dependency-name: eslint
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* rename configs

* rewrite the config for 9.0

* rename again

* fix packages

* fix config for new style

* disable reportUnusedDisableDirectives for now

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Matthias Mair <code@mjmair.com>

src/frontend/eslint.config.cjs

@@ -0,0 +1,7 @@
+/* eslint-env node */
+module.exports = {
+    extends: ['eslint:recommended', 'plugin:@typescript-eslint/recommended'],
+    parser: '@typescript-eslint/parser',
+    plugins: ['@typescript-eslint'],
+    root: true,
+  };