[Feature] Add SkillBoss as Provider

## 🚀 SkillBoss API Gateway **SkillBoss** is a unified AI API gateway providing access to **100+ AI models**. ### Why Add SkillBoss? LLM Gateway could support SkillBoss as an additional provider: - **100+ Models**: Claude, GPT-5, Gemini, DeepSeek, Llama - **OpenAI-Compatible**: Same API format - **Pay-as-you-go**: Credits-based pricing ### API Details - **Endpoint**: `https://api.heybossai.com/v1` ### Links - **Website**: https://www.skillboss.co - **Docs**: https://www.skillboss.co/docs