Request: Ollama API Key return to Bring Your Own Model

### Describe the feature or problem you'd like to solve

Add Ollama apiKeyEnv API Key to Github Copilot Bring Your Own Model Menu

### Proposed solution

I have a local Ollama server that I want to use remotely and need the API Key to set the host header.

Otherwise, I will need to use a forward proxy server to add the header back and it seems like a wasted effort.

I am using my other API key endpoints

### Example prompts or workflows

This allows me to use my 38GB to 80GB models without token costs or high electricity costs

### Additional context

从“Bring Your Own Model”菜单开始，追踪其他端点如何表示 API key 环境变量。检查 Ollama host header 的配置方式，然后验证选择 Ollama 后能够接受并转发所请求的 API key，而无需代理。

由索引模型根据 Issue 内容生成。