Add deployment path support

[emgarten]

No description provided.

[Copilot]

Pull Request Overview

Adds a new routing path to support model deployments in the chat completions proxy.

• Introduces /provider/{provider}/deployments/{model}/chat/completions endpoint.
• Delegates the new route to the existing chat_proxy handler without incorporating the model parameter.

Comments suppressed due to low confidence (1)

src/prompt_passage/proxy_app.py:65

• No tests were provided for the new deployment-specific endpoint. Add integration or unit tests to verify that requests to /deployments/{model}/chat/completions correctly forward with the intended model parameter.

@app.post("/provider/{provider}/deployments/{model}/chat/completions")