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/notices/error.html.twig

@@ -0,0 +1,34 @@
+{#
+ # Error Notice (Bootstrap 5 Override)
+ #
+ # Displays WooCommerce error notices as a Bootstrap 5 danger alert.
+ # Multiple errors are shown as a list within a single alert.
+ #
+ # Expected context:
+ #   notices - Array of notice objects, each with:
+ #     notice      - Notice HTML content (pre-sanitized via wc_kses_notice)
+ #     data        - Optional data attributes string
+ #
+ # WooCommerce PHP equivalent: notices/error.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% if notices is defined and notices|length > 0 %}
+    <div class="alert alert-danger alert-dismissible fade show woocommerce-error" role="alert">
+        <i class="bi bi-exclamation-triangle me-2" aria-hidden="true"></i>
+        {% if notices|length == 1 %}
+            {{ notices[0].notice|raw }}
+        {% else %}
+            <ul class="mb-0 ps-3">
+                {% for notice in notices %}
+                    <li {{ notice.data|default('')|raw }}>
+                        {{ notice.notice|raw }}
+                    </li>
+                {% endfor %}
+            </ul>
+        {% endif %}
+        <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="{{ __('Close') }}"></button>
+    </div>
+{% endif %}

templates/notices/notice.html.twig

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+{#
+ # Info Notice (Bootstrap 5 Override)
+ #
+ # Displays WooCommerce info/neutral notices as Bootstrap 5 alerts.
+ #
+ # Expected context:
+ #   notices - Array of notice objects, each with:
+ #     notice      - Notice HTML content (pre-sanitized via wc_kses_notice)
+ #     data        - Optional data attributes string
+ #
+ # WooCommerce PHP equivalent: notices/notice.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% if notices is defined and notices|length > 0 %}
+    {% for notice in notices %}
+        <div class="alert alert-info alert-dismissible fade show woocommerce-info"
+             {{ notice.data|default('')|raw }}
+             role="status">
+            <i class="bi bi-info-circle me-2" aria-hidden="true"></i>
+            {{ notice.notice|raw }}
+            <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="{{ __('Close') }}"></button>
+        </div>
+    {% endfor %}
+{% endif %}

templates/notices/success.html.twig

@@ -0,0 +1,27 @@
+{#
+ # Success Notice (Bootstrap 5 Override)
+ #
+ # Displays WooCommerce success notices as Bootstrap 5 success alerts.
+ #
+ # Expected context:
+ #   notices - Array of notice objects, each with:
+ #     notice      - Notice HTML content (pre-sanitized via wc_kses_notice)
+ #     data        - Optional data attributes string
+ #
+ # WooCommerce PHP equivalent: notices/success.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% if notices is defined and notices|length > 0 %}
+    {% for notice in notices %}
+        <div class="alert alert-success alert-dismissible fade show woocommerce-message"
+             {{ notice.data|default('')|raw }}
+             role="alert">
+            <i class="bi bi-check-circle me-2" aria-hidden="true"></i>
+            {{ notice.notice|raw }}
+            <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="{{ __('Close') }}"></button>
+        </div>
+    {% endfor %}
+{% endif %}