[Bug] Curl called without --max-time — requests hang indefinitely

[PyDevC]

File: lua/model_cmp/modelapi/request.lua:34-51

Introduction: Curl is called without any timeout flags. If the LLM server is unresponsive, DNS fails, or network is slow, the request hangs forever. Neovim UI becomes unresponsive.

Detailed Description: Wire config.requests.timeout_ms to curl --max-time. Also add --connect-timeout for connection failures.