实现报销材料连续预览（07-27-yang-jun-reimbursement-readiness）

server/src/services/invoiceDocumentMeta.js

@@ -0,0 +1,22 @@
+const SAFE_DOCUMENT_CATEGORIES = new Set([
+  "vat_invoice",
+  "full_vat_invoice",
+  "electronic_train_ticket",
+]);
+
+function normalizeSafeMetaString(value, maxLength = 64) {
+  if (typeof value !== "string") return null;
+  const normalized = value.trim();
+  return normalized ? normalized.slice(0, maxLength) : null;
+}
+
+function mapInvoiceDocumentMeta(invoice) {
+  const result = invoice?.ocr_result?.result_json;
+  const category = normalizeSafeMetaString(result?.documentCategory);
+  return {
+    documentCategory: SAFE_DOCUMENT_CATEGORIES.has(category) ? category : null,
+    documentSubtype: normalizeSafeMetaString(result?.documentSubtype),
+  };
+}
+
+module.exports = { mapInvoiceDocumentMeta };