Allow clients to add and manage payment methods in the portal

Currently, clients can only add a credit card by clicking a setup link that the therapist sends via email. There is no section in the client portal where clients can independently add, update, or manage their payment method on file.

Why this matters:

1. Self-service: Clients should be able to add or update their card without requiring the therapist to send them a new setup link.

2. Convenience: Clients can manage their billing info anytime, reducing back-and-forth emails.

3. Security: Clients can update expired or compromised cards on their own schedule.

4. Standard UX: Most healthcare and SaaS platforms allow clients/users to manage their own payment methods in their account settings.

Suggested implementation:

• Add a Payment Methods or Billing Settings section to the client portal

• Allow clients to add, update, and delete saved payment methods

• Show which card is set as the default for invoices

• Maintain the existing email-link flow as an alternative option

Current workaround: Therapist must manually send setup links each time a client needs to add or update a card, creating extra administrative work.