add mobile swipe for product card images and fix dev asset caching

Product cards now use CSS scroll-snap on touch devices (mobile) for
swiping between images, with dot indicators and a JS hook for active
state. Desktop keeps the existing hover crossfade via @media (hover:
hover). Dots use size differentiation (WCAG 2.2 AA compliant) with
outline rings for contrast on any background.

Also fixes: no-image placeholder (SVG icon instead of broken img),
unnecessary wrapper div for single-image cards, and dev static asset
caching (was immutable for all envs, now only prod).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PROGRESS.md

@@ -20,7 +20,54 @@
 - Transactional emails (order confirmation, shipping notification)
 - Demo content polished and ready for production
 
-**Tier 1 MVP complete.** CI pipeline done. Hosting & deployment done (including observability). PageSpeed CI done (99-100 mobile, 97+ desktop). Next up: remaining Tier 2 items (Litestream backup, e2e tests).
+**Tier 1 MVP complete.** CI pipeline done. Hosting & deployment done (including observability). PageSpeed CI done (99-100 mobile, 97+ desktop). Next up: usability fixes from user testing, then remaining Tier 2 items (Litestream backup, e2e tests).
+
+## Usability Issues (from user testing, Feb 2025)
+
+Issues found during hands-on testing of the deployed prod site on mobile and desktop.
+
+**Approach:** One issue at a time, test and verify each fix before moving on.
+
+**Principles:**
+- **Semantic, minimal HTML** — achieve everything with the simplest markup possible
+- **Progressive enhancement** — HTML and CSS first, then LiveView, JS only as a last resort
+- **Fully accessible** — WCAG 2.1 AA compliant, proper focus management, ARIA where needed, keyboard navigable
+- **Mobile-first responsive** — design for small screens first, enhance for larger viewports
+- **Appropriate interactions** — touch-friendly on mobile (swipe, tap), hover/keyboard for desktop users
+
+### Mobile / touch
+- [x] Product photos require double-tap on mobile (hover state blocks first tap)
+- [x] Product photos should be swipeable on mobile (hover-to-reveal is desktop-only)
+- [x] Product card second image: swipe to reveal on mobile (currently hover-only)
+
+### Product detail page
+- [ ] Product category breadcrumbs look bad — review styling/layout
+- [ ] Quantity selector on product page doesn't work
+- [ ] Trust badges: two different tick icons, should use sentence case not title case
+- [ ] Real product variants need testing and refinement with live data
+
+### Cart
+- [ ] Should be able to change quantity in the cart drawer (currently only on cart page?)
+- [ ] Cart drawer button → "view basket" feels redundant — streamline the flow
+
+### Navigation & links
+- [ ] Search doesn't work (modal opens but no results/functionality)
+- [ ] "Shop the collection" button/link does nothing
+- [ ] Footer "New arrivals" and "Best sellers" links don't go anywhere
+- [ ] Should be able to tap a category badge on product cards to go to that category
+- [ ] Footer social icons should match the "Find me on" icons from the contact page
+
+### Collections / all products
+- [ ] Categories on all-products page are too spaced out
+
+### Content pages
+- [ ] Hero title spacing differs between content pages (about, delivery, etc.) — contact is fine
+
+### Sale / filtering
+- [ ] Should there be a "Sale" section or filter for discounted products?
+
+### Errors
+- [ ] 404 page is broken
 
 ## Roadmap