Remove Team Payment Method

Remove the team's payment method and downgrade to Hobby plan.

Requires: MANAGE_BILLING permission (owner, admin, or billing role)

This endpoint:

1. Cancels any active Stripe subscriptions for the team
2. Downgrades the team to the Hobby plan
3. Removes the stored card from the Stripe customer

Args: team_id: Team UUID request: Payment method ID to remove auth: Authenticated user context

Returns: Success status with message