feat(orders): reopen cancelled orders only after confirmation; accurate sales

Cancelled orders:
- Moving an order out of STORNIERT is possible again, but only after a
  warning is confirmed in the status form (OrderStatusForm); without
  the confirmation the server changes nothing.
- Reopening books the counter-entry to the cancellation: goods that the
  cancellation restocked are deducted again (atomically, only if enough
  stock is left, otherwise the order stays cancelled). A later second
  cancellation therefore restocks +1 again instead of leaving +2.
- The warning states that no new payment is collected.

Dashboard figures:
- One definition of a counted sale (lib/sales.ts): not unpaid (NEU),
  not cancelled, no refunded return. Used for revenue today/month, sold
  glasses, average cart, top products/categories, revenue trend and
  repeat customers.
- "Verkaufte Gläser" previously summed every order item, including
  cancelled orders and refunded returns.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

src/i18n/dictionaries/en.ts

@@ -1356,6 +1356,8 @@ export const en: Dictionary = {
       "This order cannot be deleted — a payment or an invoice is attached to it, or it is already being processed. Invoices and payment records are subject to statutory retention. Cancel the order instead: that refunds the money, returns the goods to stock and keeps the record.",
   },
   adminOrdersPage: {
+    reopenConfirm:
+      "This order is cancelled: the goods were restocked and any payment refunded. Reopening deducts the goods from stock again — it does NOT collect a new payment, you have to arrange that yourself. Really reopen?",
     backToDashboard: "Back to dashboard",
     title: "Orders",
     searchLabel: "Search (number, email, last name)",