feat: Add AI credit topup flow for Stripe (#12988)

Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>
Co-authored-by: Pranav <pranav@chatwoot.com>

app/policies/account_policy.rb

@@ -30,4 +30,8 @@ class AccountPolicy < ApplicationPolicy
   def toggle_deletion?
     @account_user.administrator?
   end
+
+  def topup_checkout?
+    @account_user.administrator?
+  end
 end