Adds a per-letter vinyl text add-on tied to the Custom Vinyl Square item.
Customers pick a balloon shape (Heart/Star/Circle), type their message
(max 30 non-space chars, ASCII only — no emoji), and choose from 8 Google
Fonts rendered as live previews. Price updates in real time at $0.65/letter.
At checkout, vinyl orders expand to two Square line items: the 18" Shape
balloon at its catalog price and the Custom Vinyl service at the calculated
letter count price, with the font attached as a modifier.
Also adds a per-item admin toggle ("Suggest custom vinyl add-on") that shows
a promo note on any balloon's product modal pointing customers toward the
vinyl service.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
