Fix unstyled pages: rename base.html.twig to avoid parent collision

The child's templates/base.html.twig was shadowing the parent's
views/base.html.twig (full HTML page shell) because prependPath()
made Twig find the child's minimal wrapper first. Rename to
wc-base.html.twig so the parent's page shell renders correctly.

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

templates/global/breadcrumb.html.twig

@@ -2,7 +2,7 @@
  # Shop Breadcrumb (Bootstrap 5 Override)
  #
  # Replaces WooCommerce's breadcrumb with Bootstrap 5 breadcrumb component.
- # Skipped when parent theme is wrapping (base.html.twig handles breadcrumbs).
+ # Skipped when parent theme is wrapping (wc-base.html.twig handles breadcrumbs).
  #
  # Expected context (from WooCommerce woocommerce_breadcrumb()):
  #   breadcrumb  - Array of [label, url] tuples