fix(llm): add default 60s timeout to prevent hanging LLM API calls

[Jah-yee]

Summary

Adds default 60-second timeout to OpenAI client API calls to prevent indefinite hangs on network issues.

Problem

Currently, autogen creates OpenAI client API calls without a default timeout, which can cause:

• Multi-agent workflows stuck waiting forever on network issues
• No way to recover from transient network failures

Solution

Add a default timeout of 60 seconds in _create_args_from_config() when no timeout is explicitly provided by the user.

Changes

• Modified _create_args_from_config() in python/packages/autogen-ext/src/autogen_ext/models/openai/_openai_client.py
• Added 3 lines to check if timeout is not provided and set default to 60.0 seconds