Add iFlow as a new OAuth-based provider for CLIProxy.
Changes:
- Add config/base-iflow.settings.json with iFlow provider configuration
- Add iFlow to CLIProxyProvider type
- Add iFlow OAuth config (authUrl, scopes, authFlag)
- Add iFlow to provider display names, auth prefixes, and type values
- Update config-generator to support iFlow provider
- Update base-qwen.settings.json models (qwen3-coder-plus)
Co-authored-by: kaitranntt <kaitran.ntt@gmail.com>