Restrict payment setup to organization admins and owners

Only admins and owners can configure Stripe payments; team members see who in the org to ask.

What's New

Payment setup is now restricted to organization admins and owners, ensuring that sensitive billing configuration stays in experienced hands. Team members without admin or owner privileges will see a helpful banner listing the organization's admins and owners, with their names, email addresses, and roles — so everyone knows who to ask for help setting up payments.