[Feature Request] Add AIHubMix as a Provider

Motivation

AIHubMix (https://aihubmix.com) is a widely-used API aggregation platform that provides access to 300+ models from OpenAI, Anthropic, Google and others via a single API key.

What sets AIHubMix apart from similar aggregators is that it supports two distinct API protocols:

1. OpenAI-compatible format
2. Native Anthropic API format

Solution

No response

Alternatives

No response

Additional context

• AIHubMix API docs: https://docs.aihubmix.com
• OpenAI-compatible base URL: https://aihubmix.com/v1
• Anthropic-native base URL: https://aihubmix.com