Refactor ESLint config to resolve tseslint.config deprecation warnings

[rowleks]

This PR updates the ESLint configuration file (eslint.config.mjs) to fix deprecation warnings related to typescript-eslint.

Changes:

• Replaced the tseslint.config() helper function with a standard array export (export default [...]).
• Removed the deprecated extends property usage inside the config object.
• Manually spread tseslint.configs.recommendedTypeChecked into the flat config array.

Reason for Change:

The tseslint.config helper (specifically the signature accepting extends) is deprecated in newer versions of typescript-eslint. Switching to a native array export for ESLint's Flat Config format resolves the following warning:

The signature '(...configs: InfiniteDepthConfigWithExtends[]): ConfigArray' of 'tseslint.config' is deprecated.

Verification:

Run npm run lint to ensure linting still functions correctly without the warning.