feat(documents): accept selected_custom_fields in document schemas

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

src/schemas/issued-orders.schema.ts

@@ -41,6 +41,12 @@ export const CreateIssuedOrderSchema = z.object({
   // Rich-text CZ/EN sections rendered on their own PDF page (mirrors offers'
   // scope_sections — shared DocumentSectionSchema, DB-aligned limits).
   sections: z.array(DocumentSectionSchema).optional(),
+  // Positional indices of company custom fields to print on this document's
+  // PDF. Omitted/empty ⇒ none. Update schema derives via .partial().
+  selected_custom_fields: z
+    .array(z.number().int().nonnegative())
+    .max(200)
+    .optional(),
 });
 
 // Update = partial create MINUS the number: PO numbers are immutable