- Add eslint.config.js using new flat config format
- Configure @typescript-eslint/parser and plugin for TypeScript files
- Add separate config for vanilla JavaScript files (gateway/ui)
- Include Node.js and browser globals
- Enable strict rules: curly braces, no-eval, eqeqeq, etc.
- Configure TypeScript-specific rules (no-explicit-any, no-non-null-assertion)
- Add @typescript-eslint/parser and @typescript-eslint/eslint-plugin dependencies