debug: log file sizes at extraction and processing stages

Add logging to compare file sizes:
- [EXTRACT] sent to Gemini
- [CREATE_ITEM] received when creating item

This will reveal if image is being processed/changed between extraction and local processing.

backend/routers/items.py

@@ -103,7 +103,9 @@ async def extract_label(
             detail="File exceeds 10MB limit."
         )
 
+    log.info(f"[EXTRACT] Sending {len(contents)} bytes to Gemini for analysis")
     result = extract_label_info(contents, mode=mode)
+    log.info(f"[EXTRACT] Gemini returned: {type(result).__name__}")
     return result
 
 @router.post("/", response_model=schemas.Item, status_code=status.HTTP_201_CREATED)
@@ -152,6 +154,7 @@ def create_item(
         try:
             import base64
             image_bytes = base64.b64decode(item.extracted_image_bytes)
+            log.info(f"[CREATE_ITEM] Received {len(image_bytes)} bytes for photo processing (base64 decoded)")
 
             photo_result = _auto_save_photo_from_extraction(
                 item_id=db_item.id,