next-codemod: improve upgrade DX for peer dependency conflicts
- Add pre-installation peer dependency check to detect conflicts before npm install fails
- Auto-upgrade ESLint to v9+ when upgrading eslint-config-next to v16+
- Auto-upgrade @typescript-eslint/parser and @typescript-eslint/eslint-plugin to v8+ for ESLint 9 compatibility
- Suggest ESLint flat config migration when upgrading to ESLint 9
- Remove --turbopack flag from dev/build scripts for Next.js 16+ (Turbopack is now the default)
- Improve error messages with actionable guidance when installation fails
