Fix pydantic validation: use Optional[str] for API keys to make them truly optional

app/core/config.py

@@ -1,17 +1,16 @@
-from pydantic_settings import BaseSettings, SettingsConfigDict
+from pydantic_settings import BaseSettings
+from typing import Optional
 
 
 class Settings(BaseSettings):
-    model_config = SettingsConfigDict(
-        env_file=".env",
-        env_ignore_empty=True,
-        extra="ignore"
-    )
-    
-    GROQ_API_KEY: str = ""
-    OPENAI_API_KEY: str = ""
+    GROQ_API_KEY: Optional[str] = None
+    OPENAI_API_KEY: Optional[str] = None
     DATABASE_URL: str = "sqlite:///./brain_platform.db"
     ENVIRONMENT: str = "development"
 
+    class Config:
+        env_file = ".env"
+        extra = "ignore"
+
 
 settings = Settings()