F(backend): add public media derivatives pipeline

apps/gallery/api/views.py

@@ -63,6 +63,7 @@ def upload_image(request, file: UploadedFile = File(...), data: GalleryCreateSch
             alt_text=data.alt_text if data else "",
             is_public=data.is_public if data else True
         )
+        gallery_item._defer_image_processing = True
         
         # Save image
         filename = f"gallery/{uuid.uuid4().hex}.{file.name.split('.')[-1]}"