fix(config): use gpt-5.1 (actually available) not gpt-5 (deprecated)

src/utils/config.py

@@ -26,7 +26,7 @@ class Settings(BaseSettings):
     llm_provider: Literal["openai", "anthropic", "huggingface"] = Field(
         default="openai", description="Which LLM provider to use"
     )
-    openai_model: str = Field(default="gpt-5", description="OpenAI model name")
+    openai_model: str = Field(default="gpt-5.1", description="OpenAI model name")
     anthropic_model: str = Field(
         default="claude-sonnet-4-5-20250929", description="Anthropic model"
     )