Lists the Dropcontact billing invoices (Stripe-hosted) for the signed-in account, going from the app's billing settings into the Stripe customer portal and reading its invoice history. Requires an authenticated app.dropcontact.com session. Returns per invoice: date, amount, status, statusTone and hostedInvoiceUrl — an invoice.stripe.com page with its own download button, so this returns links rather than PDF files. `status` is the wording the portal shows, in whatever language it serves it; `statusTone` is the language-independent reading of the same badge ("positive" for a settled invoice). date and amount are nullable. Works in any portal language.
