feat(orders): PDF footer = issuer name+email, 'Zobrazit objednávku' button, per-currency list totals

- Issued-order PDF: drop the Vystavil/Schválil signature row; footer now shows
  'Vystavil: <name>' + 'E-mail: <email>' from the logged-in user (authData).
- IssuedOrderDetail PDF button 'Export PDF' -> 'Zobrazit objednávku' (already
  opens inline like invoices' 'Zobrazit fakturu').
- New /orders/stats + /issued-orders/stats endpoints sum order total (incl VAT)
  per currency across the active filter; rendered as 'Celkem: …' beneath both
  the received and issued lists. formatMultiCurrency lifted to a shared util.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/lib/queries/orders.ts

@@ -82,6 +82,33 @@ export const orderListOptions = (filters: {
     },
   });
 
+export interface CurrencyAmount {
+  amount: number;
+  currency: string;
+}
+
+export const orderStatsOptions = (filters: {
+  search?: string;
+  status?: string;
+  month?: number;
+  year?: number;
+}) =>
+  queryOptions({
+    queryKey: ["orders", "stats", filters],
+    queryFn: async () => {
+      const params = new URLSearchParams();
+      if (filters.search) params.set("search", filters.search);
+      if (filters.status) params.set("status", filters.status);
+      if (filters.month) params.set("month", String(filters.month));
+      if (filters.year) params.set("year", String(filters.year));
+      const qs = params.toString();
+      const data = await jsonQuery<{ totals?: CurrencyAmount[] }>(
+        `/api/admin/orders/stats${qs ? `?${qs}` : ""}`,
+      );
+      return data.totals ?? [];
+    },
+  });
+
 export const orderDetailOptions = (id: string | undefined) =>
   queryOptions({
     queryKey: ["orders", id],