Add deferred image upload support to entity creation flows:
- Roaster, roast, gear, cafe forms save images on create via
save_deferred_image helper
- Brew form accepts optional image upload
- Check-in form accepts optional cup photo
- Scan flow preserves captured image for new roasts and skips
overwriting existing roast images
- Homepage updated with image-upload component registration
- Delete handlers for brews and cups clean up associated images
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