feat(documents): accept selected_custom_fields in document schemas

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

src/schemas/invoices.schema.ts

@@ -50,6 +50,11 @@ export const CreateInvoiceSchema = z.object({
   // Rich-text CZ/EN "Obsah" sections rendered after the items on the PDF
   // (mirrors issued orders — shared DocumentSectionSchema, DB-aligned limits).
   sections: z.array(DocumentSectionSchema).optional(),
+  // Positional indices of company custom fields to print on this document's PDF.
+  selected_custom_fields: z
+    .array(z.number().int().nonnegative())
+    .max(200)
+    .optional(),
 });
 
 export const UpdateInvoiceSchema = z.object({
@@ -74,6 +79,10 @@ export const UpdateInvoiceSchema = z.object({
   paid_date: nullableIsoDateString,
   items: z.array(InvoiceItemSchema).optional(),
   sections: z.array(DocumentSectionSchema).optional(),
+  selected_custom_fields: z
+    .array(z.number().int().nonnegative())
+    .max(200)
+    .optional(),
 });
 
 export type CreateInvoiceInput = z.infer<typeof CreateInvoiceSchema>;