`lint` target in `Makefile` uses `--ext .ts` flag that was removed in ESLint v9

What happens: The lint target in Makefile runs npx eslint src --ext .ts. The project's package.json specifies "eslint": "^9.0.0", but the --ext CLI option was removed as a breaking change in ESLint v9 (it was replaced by specifying file patterns in the config file). Running make lint therefore fails. The eslint.config.js already specifies files: ["**/*.ts", ...], so the flag is both redundant and unsupported.

What should happen: The lint target should run npx eslint src (without --ext .ts), relying on the files patterns already present in eslint.config.js to select TypeScript files.