The webhook route previously assumed the backend's confirm-payment
endpoint sent the customer confirmation email; the backend assumed the
opposite. Net effect: a successful Stripe payment never triggered any
confirmation email. Consume the order snapshot confirm-payment now
returns and send it from here, matching what the checkout route already
does for a manual/Überweisung order.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Checkout now branches on payment-methods.provider: Überweisung stays
immediate/unchanged, Kreditkarte/PayPal creates a pending_payment order,
mounts Stripe's Payment Element, and defers invoice/email to a webhook-
verified confirm-payment call once the backend actually confirms payment.
Includes a PAYMENT_TEST_MODE mock provider so the whole gated pipeline is
exercisable locally without a real Stripe account.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Marco