enhancement: make chat message timeout configurable

[mrveiss]

Problem

The 30-second chat message processing timeout added in #1797 is hardcoded:

asyncio.wait_for(process_chat_message(...), timeout=30.0)

For complex LLM queries or large context windows, 30s may be insufficient. The timeout should be configurable via environment variable or config.yaml.

Suggested Fix

CHAT_TIMEOUT = float(os.environ.get("AUTOBOT_CHAT_TIMEOUT", "30.0"))
asyncio.wait_for(process_chat_message(...), timeout=CHAT_TIMEOUT)

Or use the existing config.yaml / global_config_manager pattern.

Discovered During

Implementing #1797 (chat timeout + granular error mapping)

Impact

Low — 30s default is reasonable for most use cases. Configurable for edge cases.