feat(cloud-billing): cancel subscriptions at period end on deletion mark (#13580)

## How to reproduce
In Chatwoot Cloud, mark an account for deletion from account settings
while the account has an active Stripe subscription. Before this change,
deletion marking did not explicitly mark subscriptions to stop renewing
at period end.

## What changed
This PR adds `Enterprise::Billing::CancelCloudSubscriptionsService` and
calls it from the delete action path in
`Enterprise::Api::V1::AccountsController`. The service lists only active
Stripe subscriptions for the customer and sets `cancel_at_period_end:
true` when needed. The account deletion schedule remains unchanged
(existing static 7-day behavior), and Stripe deleted-event fallback
behavior remains unchanged.

## How this was tested
Added and updated specs:
-
`spec/enterprise/services/enterprise/billing/cancel_cloud_subscriptions_service_spec.rb`
-
`spec/enterprise/controllers/enterprise/api/v1/accounts_controller_spec.rb`

Executed:
- `bundle exec rspec
spec/enterprise/services/enterprise/billing/cancel_cloud_subscriptions_service_spec.rb`
- `bundle exec rspec
spec/enterprise/controllers/enterprise/api/v1/accounts_controller_spec.rb:363`

enterprise/app/controllers/enterprise/api/v1/accounts_controller.rb

@@ -102,6 +102,8 @@ class Enterprise::Api::V1::AccountsController < Api::BaseController
     reason = 'manual_deletion'
 
     if @account.mark_for_deletion(reason)
+      cancel_cloud_subscriptions_for_deletion
+
       render json: { message: 'Account marked for deletion' }, status: :ok
     else
       render json: { message: @account.errors.full_messages.join(', ') }, status: :unprocessable_entity
@@ -125,6 +127,12 @@ class Enterprise::Api::V1::AccountsController < Api::BaseController
     render_redirect_url(session.url)
   end
 
+  def cancel_cloud_subscriptions_for_deletion
+    Enterprise::Billing::CancelCloudSubscriptionsService.new(account: @account).perform
+  rescue Stripe::StripeError => e
+    Rails.logger.warn("Failed to cancel cloud subscriptions for account #{@account.id}: #{e.class} - #{e.message}")
+  end
+
   def render_redirect_url(redirect_url)
     render json: { redirect_url: redirect_url }
   end

enterprise/app/services/enterprise/billing/cancel_cloud_subscriptions_service.rb

@@ -0,0 +1,24 @@
+class Enterprise::Billing::CancelCloudSubscriptionsService
+  pattr_initialize [:account!]
+
+  def perform
+    return if stripe_customer_id.blank?
+    return unless ChatwootApp.chatwoot_cloud?
+
+    subscriptions.each do |subscription|
+      next if subscription.cancel_at_period_end
+
+      Stripe::Subscription.update(subscription.id, cancel_at_period_end: true)
+    end
+  end
+
+  private
+
+  def subscriptions
+    Stripe::Subscription.list(customer: stripe_customer_id, status: 'active', limit: 100).data
+  end
+
+  def stripe_customer_id
+    account.custom_attributes['stripe_customer_id']
+  end
+end