fix(loyalty): use confirm modal for category deletion

Replace browser confirm() dialog with the shared confirm_modal
macro for category deletion. Matches the existing program delete
pattern. Shows warning about impact on existing transactions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/loyalty/templates/loyalty/admin/merchant-detail.html

@@ -152,7 +152,7 @@
         </div>
     </div>
 
-    <!-- Delete Confirmation Modal -->
+    <!-- Delete Program Confirmation Modal -->
     {{ confirm_modal(
         'deleteProgramModal',
         _('loyalty.admin.merchant_detail.delete_title'),
@@ -164,6 +164,18 @@
         'danger'
     ) }}
 
+    <!-- Delete Category Confirmation Modal -->
+    {{ confirm_modal(
+        'deleteCategoryModal',
+        _('loyalty.common.delete'),
+        _('loyalty.admin.merchant_detail.delete_category_message'),
+        'confirmDeleteCategory()',
+        'showDeleteCategoryModal',
+        _('loyalty.common.delete'),
+        _('loyalty.common.cancel'),
+        'danger'
+    ) }}
+
     <!-- Location Breakdown -->
     <div x-show="locations.length > 0" class="px-4 py-3 mb-8 bg-white rounded-lg shadow-md dark:bg-gray-800">
         <h3 class="mb-4 text-lg font-semibold text-gray-700 dark:text-gray-200">
@@ -287,7 +299,7 @@
                                         class="text-sm" :class="cat.is_active ? 'text-orange-500 hover:text-orange-700' : 'text-green-500 hover:text-green-700'">
                                     <span x-html="$icon(cat.is_active ? 'ban' : 'play', 'w-4 h-4')"></span>
                                 </button>
-                                <button @click="deleteCategory(cat.id)" type="button"
+                                <button @click="categoryToDelete = cat.id; showDeleteCategoryModal = true" type="button"
                                         aria-label="{{ _('loyalty.common.delete') }}"
                                         class="text-red-500 hover:text-red-700">
                                     <span x-html="$icon('trash', 'w-4 h-4')"></span>