[FEAT] Support OpenRouter

Is your feature request related to a problem? Please describe. I use OpenRouter for LLM models, but there are no option for choosing OpenRouter as LLM provider.

Describe the solution you'd like Add option for choosing OpenRouter as LLM provider.

Describe alternatives you've considered I wanted to use local Ollama models for instead but my 8GB RAM and 256GB disk say no.

Additional context None.