Proxy HTTP clients lack proper timeouts

[saketh-are]

Two proxy clients are misconfigured:

1. OpenAIProxy builds reqwest::Client::new() with no timeout (crates/services/src/response/service.rs:21). A hung upstream can stall a request indefinitely.
2. AgentProxy uses a 30s total request timeout (crates/services/src/agent/proxy.rs:46-47, .timeout(Duration::from_secs(30))). This caps the entire response including streamed bodies, truncating legitimate long streams.

Fix: Use connect + read/idle timeouts rather than a short total. Give OpenAIProxy at least a connect timeout; replace AgentProxy's total .timeout() with .connect_timeout() + an idle/read timeout so streaming isn't cut at 30s.