[FEATURE] Add Starveri API as an OpenAI-compatible custom provider example

[Lwoxs]

Hi Flowise team,

Opening this as a provider/docs request rather than assuming native support is the right shape.

Starveri API is an independent OpenAI-compatible GPT/Codex API gateway with prepaid credits, public model discovery, and model pricing advertised at about 1/3 of OpenAI-style API prices. It is not affiliated with OpenAI.

Public references:

• Docs: https://api.starveri.net/docs
• Credits / API keys: https://api.starveri.net/credits
• Public model metadata: https://api.starveri.net/models
• OpenAPI spec: https://api.starveri.net/openapi.json
• LLM discovery: https://api.starveri.net/llms.txt

Suggested setup shape if the existing OpenAI custom/compatible provider path is the right fit:

• Base URL: https://api.starveri.net/v1
• API key: issued from the Starveri credits dashboard
• Model IDs: use the public /models response

Would a Starveri custom-provider example or preset be in scope for users comparing lower-cost OpenAI-compatible GPT/Codex endpoints?