refactor: split shop_components.ex into 5 focused sub-modules

4,487-line monolith → 23-line facade + 5 modules:
- Base (inputs, buttons, cards)
- Layout (header, footer, mobile nav, shop_layout)
- Cart (drawer, items, order summary)
- Product (cards, gallery, variant selector, hero)
- Content (rich text, images, contact, reviews)

`use SimpleshopThemeWeb.ShopComponents` imports all sub-modules.
No single file over ~1,600 lines now.

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

PROGRESS.md

@@ -208,6 +208,15 @@ Codebase analysis identified ~380 lines of duplication across LiveViews, templat
 
 See: [docs/plans/dry-refactor.md](docs/plans/dry-refactor.md) for full analysis and plan
 
+### Shop Page Integration Tests
+**Status:** Follow-up
+
+Home, product detail, and cart pages have no LiveView integration tests. Collection and content pages are well-covered (16 and 10 tests respectively). Priority order by logic complexity:
+
+1. **Product detail page** — variant selection, add-to-cart, gallery, breadcrumb
+2. **Cart page** — cart items, quantity changes, order summary, checkout link
+3. **Home page** — hero section, featured products, category nav (mostly presentational)
+
 ### Page Editor
 **Status:** Future (Tier 4)