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/routes/admin/quotations.ts

@@ -42,7 +42,6 @@ export default async function quotationsRoutes(
         search,
         status: query.status ? String(query.status) : undefined,
         customer_id: query.customer_id ? Number(query.customer_id) : undefined,
-        has_order: query.has_order ? String(query.has_order) : undefined,
       });
 
       return paginated(