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/breadcrumb.html.twig

@@ -0,0 +1,37 @@
+{#
+ # 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).
+ #
+ # Expected context (from WooCommerce woocommerce_breadcrumb()):
+ #   breadcrumb  - Array of [label, url] tuples
+ #   wrap_before - Opening HTML (ignored, we use Bootstrap markup)
+ #   wrap_after  - Closing HTML (ignored)
+ #   before      - Before each item (ignored)
+ #   after       - After each item (ignored)
+ #   delimiter   - Between items (ignored, Bootstrap uses CSS)
+ #
+ # WooCommerce PHP equivalent: global/breadcrumb.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% if breadcrumb is defined and breadcrumb|length > 0 %}
+    <nav aria-label="{{ __('Breadcrumb') }}">
+        <ol class="breadcrumb">
+            {% for crumb in breadcrumb %}
+                {% if not loop.last and crumb[1] is defined and crumb[1] %}
+                    <li class="breadcrumb-item">
+                        <a href="{{ crumb[1]|esc_url }}">{{ crumb[0]|esc_html }}</a>
+                    </li>
+                {% else %}
+                    <li class="breadcrumb-item active" aria-current="page">
+                        {{ crumb[0]|esc_html }}
+                    </li>
+                {% endif %}
+            {% endfor %}
+        </ol>
+    </nav>
+{% endif %}