add-provider-doc

Create usage docs in English and Chinese MDX files, update the environment variable documentation, add the provider's variables to all three Dockerfiles and .env.example, then prepare cover and screenshot images hosted on the CDN.

You must update the provider usage MDX docs (EN and CN), the model-provider environment variable docs (EN and CN), Dockerfile, Dockerfile.database, Dockerfile.pglite, and .env.example.

No, never include real API keys in documentation. Always use placeholders following the provider's key format, such as a prefix followed by masked characters.

Document the API key variable as required with a description and example format, and the model list variable as optional, explaining the plus/minus syntax for adding or hiding models.

You need a cover image, three to four API dashboard screenshots from the provider, and two to three configuration screenshots, all hosted on the LobeHub CDN.