Developer docs: API reference and integration guides

API reference

• Grouped by OpenAI Chat, OpenAI Responses, Anthropic and Gemini protocols

• Each group includes list-models endpoints, parameter tables and request examples

• Added documentation for the @ routing-strategy suffix

Integration guides

• Added installation, configuration and troubleshooting steps for CC Switch, Sider, Pi and other tools

• API keys can be viewed in the console at any time instead of only once at creation

Policies

• Added a refund policy page