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/quantity-input.html.twig

@@ -0,0 +1,74 @@
+{#
+ # Quantity Input (Bootstrap 5 Override)
+ #
+ # Replaces WooCommerce's quantity input with a Bootstrap 5 input-group
+ # featuring decrement/increment buttons.
+ #
+ # Expected context (from WooCommerce woocommerce_quantity_input()):
+ #   input_id    - Input element ID
+ #   input_name  - Input element name attribute
+ #   input_value - Current quantity value
+ #   min_value   - Minimum allowed quantity
+ #   max_value   - Maximum allowed quantity (0 = no max)
+ #   step        - Step increment
+ #   placeholder - Placeholder text
+ #   inputmode   - Input mode (e.g., 'numeric')
+ #   classes     - CSS class(es) for the input
+ #   readonly    - Whether input is read-only
+ #   type        - Input type attribute
+ #   args        - Additional args (product_name for accessible label)
+ #   autocomplete - Autocomplete attribute value
+ #
+ # WooCommerce PHP equivalent: global/quantity-input.php
+ #
+ # @package WcBootstrap
+ # @since 0.1.0
+ #}
+
+{% set label = args.product_name is defined and args.product_name
+    ? __('%s quantity')|format(args.product_name)
+    : __('Quantity')
+%}
+
+<div class="quantity input-group input-group-sm" style="max-width: 140px;">
+    {{ do_action('woocommerce_before_quantity_input_field') }}
+
+    <label class="visually-hidden" for="{{ input_id|esc_attr }}">{{ label|esc_attr }}</label>
+
+    {% if not readonly %}
+        <button type="button"
+                class="btn btn-outline-secondary wc-qty-minus"
+                aria-label="{{ __('Decrease quantity') }}"
+                data-target="#{{ input_id|esc_attr }}">
+            <i class="bi bi-dash" aria-hidden="true"></i>
+        </button>
+    {% endif %}
+
+    <input type="{{ type|default('number')|esc_attr }}"
+           {% if readonly %}readonly="readonly"{% endif %}
+           id="{{ input_id|esc_attr }}"
+           class="form-control text-center {{ classes is iterable ? classes|join(' ')|esc_attr : classes|default('')|esc_attr }}"
+           name="{{ input_name|esc_attr }}"
+           value="{{ input_value|esc_attr }}"
+           aria-label="{{ __('Product quantity')|esc_attr }}"
+           min="{{ min_value|esc_attr }}"
+           {% if max_value is defined and max_value > 0 %}max="{{ max_value|esc_attr }}"{% endif %}
+           {% if not readonly %}
+               step="{{ step|esc_attr }}"
+               placeholder="{{ placeholder|esc_attr }}"
+               inputmode="{{ inputmode|default('numeric')|esc_attr }}"
+               autocomplete="{{ autocomplete|default('on')|esc_attr }}"
+           {% endif %}
+    />
+
+    {% if not readonly %}
+        <button type="button"
+                class="btn btn-outline-secondary wc-qty-plus"
+                aria-label="{{ __('Increase quantity') }}"
+                data-target="#{{ input_id|esc_attr }}">
+            <i class="bi bi-plus" aria-hidden="true"></i>
+        </button>
+    {% endif %}
+
+    {{ do_action('woocommerce_after_quantity_input_field') }}
+</div>