Send a dedicated email for a switched Überweisung payment, not the full order-confirmation

New sendPaymentSwitchedEmail() — sent instead of sendOrderConfirmationEmail()
when confirmPaymentEmail.ts sees order.paymentSwitchedAt set. Resending the
full order-confirmation (with its invoice re-attached) after a payment-method
switch read like a brand-new purchase; this is a short, dedicated "Zahlung
erhalten" confirmation instead, matching the order-status-email shape.

Also bumps @einfach-produktiv/invoicing to 0.2.8, fixing a font-path bug
that broke every invoice PDF render inside the Payload backend specifically.

app/lib/payload.ts

@@ -838,7 +838,8 @@ export type EmailTemplateType =
   | "order-returned"
   | "order-tracking-added"
   | "order-tracking-corrected"
-  | "order-delivered";
+  | "order-delivered"
+  | "payment-method-switched";
 
 type PayloadEmailTemplate = {
   type: EmailTemplateType;