Migrate deprecated .eslintrc.json to Flat Config for ESLint 10 compatibility

[saschaszott]

With PR #4823, ESLint was updated to version 9. This version of ESLint introduced changes in configuration: ESLint now supports flat config files (eslint.config.*) alongside the traditional .eslintrc.json (which is now deprecated).

While .eslintrc.json is still supported in ESLint 9, ESLint 10 will only support flat config files (see https://eslint.org/blog/2025/10/whats-coming-in-eslint-10.0.0/#removal-of-eslintrc-functionality).

To ensure future compatibility and avoid migration issues, we should proactively convert our existing .eslintrc.json configuration to the new flat config format.

[JorgeEscire]

Hi @tdonohue, I'm a partner at @jtimal, could you please assign me this issue to work on?

[tdonohue]

Sure @JorgeEscire ! Thanks for volunteering