refactor: strip EXIF orientation before Gemini analysis for coordinate accuracy

Instead of transforming coordinates after Gemini returns crop_bounds, strip EXIF
orientation from image before sending to Gemini. This ensures:
- Gemini analyzes the same raw image as our backend
- crop_bounds are in raw image coordinate space
- No coordinate transformation needed
- Works for all images (with or without EXIF)

Added strip_exif_orientation() utility that removes orientation tag and
re-encodes image. Used in extract_label endpoint before sending to Gemini.

backend/routers/items.py

@@ -10,7 +10,7 @@ from slowapi.util import get_remote_address
 from pathlib import Path
 from .. import models, schemas, auth
 from ..database import get_db
-from ..services.image_processing import ImageProcessor
+from ..services.image_processing import ImageProcessor, strip_exif_orientation
 from ..services.image_storage import save_image, get_unique_filename
 from ..logger import log
 
@@ -104,8 +104,12 @@ 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)
+    # Strip EXIF orientation so Gemini analyzes raw image (not rotated)
+    # Backend will process the same raw image
+    contents_no_exif = strip_exif_orientation(contents)
+    log.info(f"[EXTRACT] Sending {len(contents_no_exif)} bytes to Gemini (EXIF orientation stripped)")
+
+    result = extract_label_info(contents_no_exif, mode=mode)
     log.info(f"[EXTRACT] Gemini returned: {type(result).__name__}")
     return result