Sharper product cards, a badge, and a variant picker on every product tool

Four changes across the assistant's three product cards, from the same round of polish.

• Product carousel images now bleed to the card's edges. No more inset margin around the photo: it touches the card's left, right, and top edges, with the top corners rounded to match the card and the bottom staying square where the title and pitch continue.
• The carousel can now carry a badge. The assistant can flag a product with a short label: a pill shown over the top-left corner of its photo, e.g. "On sale," or a routine-step callout like "Cleanser" or "Moisturizer" when it's presenting a multi-step routine. It's optional and appears only when the assistant has something worth flagging, up to 24 characters.
• The variant picker is now on the product detail page and the comparison table too. Product detail already showed one product in full and comparison showed several side by side; neither let a shopper switch color or size without asking the assistant again. Both now have the same picker the carousel already had: switching updates that product's photo and price instantly, no reload, and an option that's out of stock shows disabled.
• On the product detail page, "Add to cart" and "View product" now always appear together. Previously you'd see only one or the other, depending on whether the product had multiple variants. Add to cart now always acts on whichever variant is selected, and is disabled when that variant is out of stock; View product, the link to the item on your own site, sits right next to it.