Support configuring timeouts for genai chat client requests

[ragnaroh-nrk]

We currently have to create our own Client bean if we want to configure a timeout for chat client requests. This could perhaps be configurable through GoogleGenAiConnectionProperties?

[Red-Mal]

I'd like to take this one on. Before opening a PR, one design question worth settling.

I've confirmed the underlying google-genai SDK version this module pins (1.58.0) honors HttpOptions.timeout on the live call path — it derives an OkHttpClient with callTimeout(...) per request — so wiring it through is viable and not a silent no-op.

My plan is to expose it as a Duration on GoogleGenAiConnectionProperties (spring.ai.google.genai.timeout) and apply it to the Client via HttpOptions.builder().timeout(...). I put it at the connection level rather than under a chat sub-prefix because the timeout is set on the shared SDK Client, so it applies to embedding calls as well, not just chat — a chat-scoped property would be misleading about what it actually affects.

Does that placement sound right, or would you prefer it scoped differently? Happy to adjust before submitting.

[ragnaroh-nrk]

Sounds good to me. I’m not in a position to make any decisions, though.