Raise default QUESTION_TIMEOUT to 500s for gateway stalls

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

gaia_agent/config.py

@@ -52,7 +52,7 @@ class Settings(BaseSettings):
     # without tools. Bounds worst-case latency on research-heavy questions.
     max_tool_rounds: int = 3
     recursion_limit: int = 40
-    question_timeout: int = 300
+    question_timeout: int = 500
 
 
 @lru_cache(maxsize=1)