Implement Phase 2: product archive and shop loop templates (Bootstrap 5)

Add 15 Twig template overrides for the product archive and shop loop:
- archive-product: 3+9 grid layout with optional filter sidebar
- content-product: card component with hook-based content injection
- content-product-cat: category card with thumbnail
- product-searchform: input-group with search icon button
- loop/loop-start, loop-end: responsive row-cols grid
- loop/header: archive title with description hook
- loop/result-count: showing X-Y of Z with aria-relevant
- loop/orderby: form-select-sm sort dropdown
- loop/pagination: delegates to components/pagination.html.twig
- loop/no-products-found: alert-info empty state
- loop/add-to-cart: btn-primary-sm with AJAX data attributes
- loop/price: fw-semibold with sale/regular markup
- loop/rating: Bootstrap Icon stars (full, half, empty)
- loop/sale-flash: badge bg-danger positioned overlay

CSS additions: product card hover, sale badge z-index, star rating sizing,
price del/ins styling, WooCommerce grid reset.

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

PLAN.md

@@ -531,21 +531,21 @@ Track completion per file. Mark with `[x]` when done.
 
 ### Phase 2 -- Archive & Loop
 
-- [ ] `archive-product.html.twig`
-- [ ] `content-product.html.twig`
-- [ ] `content-product-cat.html.twig`
-- [ ] `product-searchform.html.twig`
-- [ ] `loop/loop-start.html.twig`
-- [ ] `loop/loop-end.html.twig`
-- [ ] `loop/header.html.twig`
-- [ ] `loop/result-count.html.twig`
-- [ ] `loop/orderby.html.twig`
-- [ ] `loop/pagination.html.twig`
-- [ ] `loop/no-products-found.html.twig`
-- [ ] `loop/add-to-cart.html.twig`
-- [ ] `loop/price.html.twig`
-- [ ] `loop/rating.html.twig`
-- [ ] `loop/sale-flash.html.twig`
+- [x] `archive-product.html.twig`
+- [x] `content-product.html.twig`
+- [x] `content-product-cat.html.twig`
+- [x] `product-searchform.html.twig`
+- [x] `loop/loop-start.html.twig`
+- [x] `loop/loop-end.html.twig`
+- [x] `loop/header.html.twig`
+- [x] `loop/result-count.html.twig`
+- [x] `loop/orderby.html.twig`
+- [x] `loop/pagination.html.twig`
+- [x] `loop/no-products-found.html.twig`
+- [x] `loop/add-to-cart.html.twig`
+- [x] `loop/price.html.twig`
+- [x] `loop/rating.html.twig`
+- [x] `loop/sale-flash.html.twig`
 
 ### Phase 3 -- Single Product