fix: replace all native confirm() dialogs with styled modal macros

Migrated ~68 native browser confirm() calls across 74 files to use the
project's confirm_modal/confirm_modal_dynamic Jinja2 macros, providing
consistent styled confirmation dialogs instead of plain browser popups.

Modules updated: core, tenancy, cms, marketplace, messaging, billing,
customers, orders, cart. Uses danger/warning/info variants and
double-confirm pattern for destructive delete operations.

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

app/modules/billing/static/store/js/billing.js

@@ -22,6 +22,8 @@ function storeBilling() {
         showTiersModal: false,
         showAddonsModal: false,
         showCancelModal: false,
+        showCancelAddonConfirm: false,
+        pendingCancelAddon: null,
         showSuccessMessage: false,
         showCancelMessage: false,
         showAddonSuccessMessage: false,
@@ -172,10 +174,6 @@ function storeBilling() {
         },
 
         async cancelAddon(addon) {
-            if (!confirm(`Are you sure you want to cancel ${addon.addon_name}?`)) {
-                return;
-            }
-
             try {
                 await apiClient.delete(`/store/billing/addons/${addon.id}`);
                 Utils.showToast(I18n.t('billing.messages.addon_cancelled_successfully'), 'success');