fix: bridge Azure Chat tools through Responses

[voodoohop]

Summary

• Adds opt-in x-portkey-chat-completions-api: responses routing for Azure Chat requests that use modern function tools with reasoning, including the model's default reasoning effort.
• Maps the Chat Completions contract through Azure /openai/v1/responses: text/image/file messages, completed tool rounds, multiple calls, tool choice, structured output, JSON/SSE responses, refusal, errors, and usage.
• Keeps explicit reasoning_effort: none on native Chat and rejects Chat fields without a safe Responses equivalent instead of silently dropping them.
• Does not expose Responses-only state or features.

Why

Azure GPT-5.5/5.6 rejects function tools plus reasoning on /chat/completions; the equivalent Responses request succeeds. Keeping the bounded compatibility bridge in the gateway avoids provider-specific translation in downstream APIs.

Testing

• Focused Jest suite passes (8/8).
• Gateway build and pre-push application smoke test pass; existing unrelated TypeScript warnings remain.
• Live Azure JSON, SSE, file input, function-call continuation, and multiple tool events returned 200.
• Live Azure confirmed logprobs is incompatible with reasoning, so the bridge returns an explicit 400 for it.

Related: pollinations/pollinations#13072, pollinations/pollinations#13254