Feature Request: OpenRouter Embeddings Support

Problem

OpenViking currently supports embedding providers: openai, volcengine, vikingdb, jina.

However, OpenRouter (https://openrouter.ai) provides many free and paid embedding models that could be used.

Issue

When trying to use OpenRouter with the openai provider:

• OpenRouter requires custom base_url (https://openrouter.ai/api/v1)
• Some models require specific providers (google-ai-studio, nvidia, etc.)
• OpenAI SDK compatible but needs extra configuration

Request

Add OpenRouter as a supported embedding provider, or add ability to:

1. Specify custom base_url
2. Add custom headers (HTTP-Referer, X-OpenRouter-Title)

Example Models Available

• openai/text-embedding-ada-002
• openai/text-embedding-3-small
• google/gemini-embedding-001
• nvidia/llama-nemotron-embed-vl-1b-v2:free (FREE!)

Thank you!