v1.7.0: fix offer created_at override, invoice PDF translations, remove has_order filter

- Add created_at to offer create/update schemas so user-selected date is stored instead of always defaulting to now()
- Translate payment method in invoice PDF based on language (Příkazem → Bank transfer, etc.)
- Add order_date and cnb_rate translation keys, replace hardcoded inline strings
- Remove duplicate has_order filter from offers backend route

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/admin/lib/queries/offers.ts

@@ -73,7 +73,6 @@ export const offerListOptions = (filters: {
   perPage?: number;
   status?: string;
   customer_id?: number;
-  has_order?: string;
 }) =>
   queryOptions({
     queryKey: ["offers", "list", filters],
@@ -87,7 +86,6 @@ export const offerListOptions = (filters: {
       if (filters.status) params.set("status", filters.status);
       if (filters.customer_id)
         params.set("customer_id", String(filters.customer_id));
-      if (filters.has_order) params.set("has_order", filters.has_order);
       const qs = params.toString();
       return paginatedJsonQuery(`/api/admin/offers${qs ? `?${qs}` : ""}`);
     },