fix: 统一文档解析文件格式校验

- 统一知识库和工作流支持格式并增加前后端上传拦截

- 拒绝 XLS 与伪装 XLSX，避免空内容解析成功

easyflow-ui-admin/app/src/utils/document-parse-file-policy.ts

@@ -0,0 +1,83 @@
+import { $t } from '#/locales';
+
+const OLE2_SIGNATURE = [208, 207, 17, 224, 161, 177, 26, 225];
+
+const supportedExtensions = Object.freeze([
+  'txt',
+  'pdf',
+  'docx',
+  'md',
+  'pptx',
+  'xlsx',
+  'csv',
+]);
+const supportedExtensionSet = new Set(supportedExtensions);
+const supportedTypeLabel = supportedExtensions
+  .map((extension) => extension.toUpperCase())
+  .join('、');
+
+function extensionOf(fileName: string) {
+  const normalizedName = String(fileName || '')
+    .trim()
+    .toLowerCase();
+  const dotIndex = normalizedName.lastIndexOf('.');
+  return dotIndex === -1 ? '' : normalizedName.slice(dotIndex + 1);
+}
+
+function supports(fileName: string) {
+  return supportedExtensionSet.has(extensionOf(fileName));
+}
+
+async function validateFiles(files: File[]) {
+  for (const file of files) {
+    const extension = extensionOf(file.name);
+    if (!supportedExtensionSet.has(extension)) {
+      throw new Error(
+        $t('message.upload.unsupportedFileType', {
+          fileName: file.name,
+          types: supportedTypeLabel,
+        }),
+      );
+    }
+    if (extension !== 'xlsx') {
+      continue;
+    }
+    const prefix = new Uint8Array(await file.slice(0, 8).arrayBuffer());
+    if (hasZipSignature(prefix)) {
+      continue;
+    }
+    const messageKey = startsWith(prefix, OLE2_SIGNATURE)
+      ? 'message.upload.legacyExcelAsXlsx'
+      : 'message.upload.invalidXlsx';
+    throw new Error($t(messageKey, { fileName: file.name }));
+  }
+}
+
+/**
+ * 知识库导入与工作流文档解析共用的文件格式策略。
+ */
+export const DocumentParseFilePolicy = Object.freeze({
+  accept: supportedExtensions.map((extension) => `.${extension}`).join(','),
+  supportedExtensions,
+  supportedTypeLabel,
+  supports,
+  validateFiles,
+});
+
+function hasZipSignature(prefix: Uint8Array) {
+  return (
+    prefix.length >= 4 &&
+    prefix[0] === 80 &&
+    prefix[1] === 75 &&
+    ((prefix[2] === 3 && prefix[3] === 4) ||
+      (prefix[2] === 5 && prefix[3] === 6) ||
+      (prefix[2] === 7 && prefix[3] === 8))
+  );
+}
+
+function startsWith(prefix: Uint8Array, signature: number[]) {
+  return (
+    prefix.length >= signature.length &&
+    signature.every((value, index) => prefix[index] === value)
+  );
+}