feat: add OpenRouter api

[cubxxw]

This pull request introduces support for the OpenRouter AI provider, including configuration settings, API integration, and UI updates. The changes span multiple files to ensure seamless integration and functionality.

Key Changes:

Configuration and Environment:

• Added OpenRouter configuration settings in .env.example to allow setting up API keys, base URL, site URL, site name, and additional models.

Backend Integration:

• Enhanced proxy-server.js to include detailed logging and error handling for Huoshan API requests and responses.
• Integrated OpenRouter API calls in aiService.ts, including methods for handling requests and responses, and added support for additional models via environment variables. [1] [2] [3] [4] [5]

Frontend Updates:

• Updated AISettings.tsx to include new tabs and forms for configuring Huoshan, Qwen, and OpenRouter settings. [1] [2] [3]
• Modified AddPromptModal.tsx to add OpenRouter models to the selectable options.

Type Definitions:

• Updated index.ts to include new LLM models and AI providers for OpenRouter. [1] [2]