Make the timeout of `Converstaion.run` configurable

[cizezsy]

The current the timeout of Conversation.run() is the default value of 3600 seconds (see https://github.com/OpenHands/benchmarks/blob/main/benchmarks/utils/fake_user_response.py#L146 and https://github.com/OpenHands/software-agent-sdk/blob/main/openhands-sdk/openhands/sdk/conversation/impl/remote_conversation.py#L870), and it cannot be configured. When the model API is slow, evaluations such as SWE-bench can easily exceed the 3600-second limit and fail due to timeout. It would be helpful to make this timeout configurable—for example through an environment variable—so users can adjust it based on their setup without modifying the source code.