Embeddings failure with 404 return

**Describe the bug**
Embeddings always failure with 404.

**To Reproduce**
run example embeeding code

**Additional context**
It seems like an upstream issue https://github.com/pepperoni21/ollama-rs/issues/85

The issue points to an upstream problem in the ollama-rs library. First, locate the embeddings code in the langchain-rust project, likely in a module like `embeddings` or `ollama`. Check the HTTP client calls and error handling for 404 responses. Review the linked upstream issue to understand the root cause. Determine if a workaround or fix can be applied in langchain-rust, or if it requires waiting for an ollama-rs update.

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