Implement Phase 1: global templates and notices (Bootstrap 5)

Add 9 Twig template overrides for WooCommerce's global and notice templates:
- global/wrapper-start, wrapper-end: conditional container with _theme_wrapped
- global/breadcrumb: Bootstrap breadcrumb component with aria-current
- global/sidebar: offcanvas-lg for mobile, standard aside for desktop
- global/quantity-input: input-group with +/- buttons
- global/form-login: responsive form with form-control, form-check
- notices/notice, error, success: Bootstrap alert-dismissible with icons

Supporting changes:
- assets/js/quantity.js: +/- button handler respecting min/max/step
- assets/css/wc-bootstrap.css: WooCommerce notice fallback styles, spinner removal
- functions.php: register quantity.js script

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

templates/global/wrapper-end.html.twig

@@ -0,0 +1,18 @@
+{#
+ # Content Wrapper End (Bootstrap 5 Override)
+ #
+ # Closes the wrapper divs opened by wrapper-start.html.twig.
+ #
+ # WooCommerce PHP equivalent: global/wrapper-end.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% set _wrapped = _theme_wrapped is defined and _theme_wrapped %}
+
+{% if not _wrapped %}
+        </main>
+    </div>
+</div>
+{% endif %}