update: upload fix

backend/app/services/llm/base.py

@@ -6,13 +6,16 @@ from app.schemas.transaction import TransactionExtractItem
 
 
 class BaseLLMProvider(ABC):
-    """Abstract base for LLM vision providers. Each provider implements extract_from_image."""
+    """Abstract base for LLM providers. Supports optional model override."""
+
+    def __init__(self, model_override: str | None = None):
+        self._model_override = model_override
 
     @abstractmethod
     async def extract_from_image(self, image_bytes: bytes) -> list[TransactionExtractItem]:
-        """
-        Analyze a billing screenshot and return structured transaction list.
-        :param image_bytes: Raw image file content (PNG/JPEG)
-        :return: List of extracted transactions (may be empty or partial on failure)
-        """
+        pass
+
+    @abstractmethod
+    async def chat(self, system: str, user: str) -> str:
+        """Plain text chat (for inference/reasoning tasks like report generation)."""
         pass