Redesign cart and collections, fix product pagination

- Cart drawer: single-column layout matching the site — no bag icon,
  no dividers, square images, tighter type, discount code form,
  estimated total, and a Go to Checkout button
- Cart: per-line loading state so one row's update no longer disables
  every other row or the checkout button
- Discounts: cartDiscountCodesUpdate mutation plus discountCodes on the
  cart fragment, wired to an applyDiscountCode store action
- Products: fix "load more" returning the same first page — the query
  now takes an `after` cursor and getProductsPage exposes pageInfo
- Collections: cards match the product cards (no border, radius, blurb,
  or CTA row) at 4-up on desktop and 2-up on mobile; section headers
  match the products section
- Shop Pay: cart permalink with payment=shop_pay instead of the hosted
  shop-js element
- Buttons converted to the shadcn Button component throughout
- PDP: swipeable image carousel with dots on mobile, sticky info column,
  colour swatches never fall back to variant photos
- Rename the store from Stride to Shop; larger header wordmark

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jWbNNJLksC1QG8z8845FX

graphql/products.js

@@ -103,8 +103,8 @@ export const ProductFragment = `
 // Get multiple products
 export const GET_PRODUCTS_QUERY = `
   ${ProductFragment}
-  query GetProducts($first: Int!, $query: String, $sortKey: ProductSortKeys, $reverse: Boolean) {
-    products(first: $first, query: $query, sortKey: $sortKey, reverse: $reverse) {
+  query GetProducts($first: Int!, $after: String, $query: String, $sortKey: ProductSortKeys, $reverse: Boolean) {
+    products(first: $first, after: $after, query: $query, sortKey: $sortKey, reverse: $reverse) {
       edges {
         node {
           ...ProductFragment