Fix billing history page errors after Stripe gem upgrade

- Replace deprecated account_balance with balance on Customer objects
- Replace deprecated date with created on Invoice objects

These API attribute changes in the newer Stripe gem were causing
NoMethodError exceptions on the billing history page.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: drusepth

app/views/subscriptions/history.html.erb

@@ -73,9 +73,9 @@
             <% @stripe_invoices.first(10).each do |invoice| %>
               <tr>
                 <td>
-                  <%= Time.at(invoice.date).strftime("%B %d, %Y") %><br />
-                  at <%= Time.at(invoice.date).strftime("%I:%M %p") %><br />
-                  <%= '(Pending)' if Time.at(invoice.date) > Time.now %>
+                  <%= Time.at(invoice.created).strftime("%B %d, %Y") %><br />
+                  at <%= Time.at(invoice.created).strftime("%I:%M %p") %><br />
+                  <%= '(Pending)' if Time.at(invoice.created) > Time.now %>
                 </td>
                 <td>
                   <ul>