Support Stripe Link payment method on the platform

Problem Statement

Stripe's Link payment method syncs correctly to Pelcro's DB, but it is not displayed on the platform (e.g., on the customer's payment methods list). Link is also not listed as supported in our docs (https://docs.pelcro.com/docs/stripe#supported-payment-methods), so the behavior is currently unofficial and inconsistent: the data exists, but admins can't see or work with it.

User Story

As an admin/client, I want Link payment methods saved through Stripe to appear on the customer record, so that I can see how a customer is paying and allow customers who have Link as the only payment method to pay invoices correctly

Definition of Done

- A Link payment method synced from Stripe is displayed on the platform wherever other payment methods appear (customer payment methods, subscription details), with a clear label.

- Link is usable as the payment source for subscription renewals and invoice payments, or its limitations are explicitly documented.

- Existing Link payment methods already synced to the DB display correctly with no re-sync or backfill needed (or a backfill is provided if required).