fix: resolve Pydantic v2 compatibility and conftest path issues

- Remove duplicate Config class from BaseAITBCConfig (Pydantic v2 compatibility)
- Update conftest.py to use DATA_DIR and LOG_DIR constants directly
- Fix TypeError: get_log_path() missing required argument
- Tests now run successfully with PYTHONPATH set

aitbc/config.py

@@ -41,12 +41,6 @@ class BaseAITBCConfig(BaseSettings):
         default="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
         description="Log format string"
     )
-    
-    class Config:
-        """Pydantic configuration"""
-        env_file = str(ENV_FILE)
-        env_file_encoding = "utf-8"
-        case_sensitive = False
 
 
 class AITBCConfig(BaseAITBCConfig):