Add constructor timeout support

[tanyav2]

Summary

• add constructor-level timeout support to TinfoilAI and AsyncTinfoilAI
• preserve OpenAI's default timeout behavior by forwarding NOT_GIVEN when callers omit it
• add isolated unit tests covering sync and async timeout passthrough

Testing

• uv run pytest tests/test_constructor_timeout.py
• uv run pytest -m 'not integration'

Notes

• this fixes the constructor compatibility issue for timeout
• this PR intentionally does not add base_url passthrough, since the secure client pins transport to the verified enclave endpoint

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Summary by cubic

Add constructor timeout support to TinfoilAI and AsyncTinfoilAI. We pass timeout to the underlying openai client, or NOT_GIVEN when omitted, to preserve default timeout behavior.

^{Written for commit 91aaddc. Summary will update on new commits.}

[cubic-dev-ai]

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