Add ZenMux as a dynamic provider

[henryhe1993]

ZenMux is a rapidly growing LLM provider that offers 100+ OpenAI-Compatible models, 50+ Anthropic API Compatible models.
Hope to integrate ZenMux as a dynamic provider for easier use.

[jiam03]

ZenMux has been extremely valuable, providing a convenient way to connect to and evaluate a wide range of AI models. We would greatly appreciate it if support for ZenMux could be added to the RooCode.

Thank you.