- Remove Reference Size input fields from customer design page
- Rulers now use product.referenceWidthCm and product.referenceHeightCm
- Reference size is set by admin when editing product (not customer)
- Simplify Add to bag validation - only check for design elements
- Remove reference size state from DesignCanvas component
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>