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/templates/billing/merchant/subscription-detail.html

@@ -1,5 +1,6 @@
 {# app/modules/billing/templates/billing/merchant/subscription-detail.html #}
 {% extends "merchant/base.html" %}
+{% from 'shared/macros/modals.html' import confirm_modal %}
 
 {% block title %}Subscription Details{% endblock %}
 
@@ -119,7 +120,7 @@
                             <span class="inline-block mt-3 px-3 py-1 text-xs font-semibold text-purple-700 dark:text-purple-400 bg-purple-100 dark:bg-purple-900/30 rounded-full">Current Plan</span>
                         </template>
                         <template x-if="!t.is_current">
-                            <button @click="changeTier(t.code)"
+                            <button @click="pendingTierCode = t.code; showChangeTierConfirm = true"
                                     :disabled="changingTier"
                                     class="mt-3 inline-flex items-center px-4 py-2 text-sm font-medium text-white rounded-lg transition-colors disabled:opacity-50"
                                     :class="t.can_upgrade ? 'bg-purple-600 hover:bg-purple-700' : 'bg-gray-600 hover:bg-gray-700'"
@@ -133,6 +134,9 @@
 
     </div>
 </div>
+
+<!-- Change Tier Confirm Modal -->
+{{ confirm_modal('changeTierConfirm', 'Change Plan', 'Are you sure you want to change your plan to this tier? Your billing will be adjusted accordingly.', 'changeTier(pendingTierCode)', 'showChangeTierConfirm', 'Change Plan', 'Cancel', 'warning') }}
 {% endblock %}
 
 {% block extra_scripts %}
@@ -145,6 +149,8 @@ function merchantSubscriptionDetail() {
         subscription: null,
         availableTiers: [],
         changingTier: false,
+        showChangeTierConfirm: false,
+        pendingTierCode: null,
 
         init() {
             this.loadSubscription();
@@ -182,8 +188,6 @@ function merchantSubscriptionDetail() {
         },
 
         async changeTier(tierCode) {
-            if (!confirm(`Are you sure you want to change your plan to this tier?`)) return;
-
             this.changingTier = true;
             this.error = null;
             this.successMessage = null;