feat: 完善知识库、策略预览与OnlyOffice集成，增强后端启动依赖检查

web/src/views/scripts/knowledgePreviewMode.js

@@ -0,0 +1,21 @@
+const ONLYOFFICE_EXTENSIONS = new Set(['docx', 'xlsx', 'pptx'])
+
+function supportsOnlyOfficePreview(document) {
+  return ONLYOFFICE_EXTENSIONS.has(String(document?.extension || '').toLowerCase())
+}
+
+export function resolveKnowledgePreviewMode(document, options = {}) {
+  if (!document) {
+    return 'none'
+  }
+
+  if (supportsOnlyOfficePreview(document) && options.onlyOfficeAvailable) {
+    return 'onlyoffice'
+  }
+
+  return document.previewKind || 'unsupported'
+}
+
+export function canUseOnlyOfficePreview(document) {
+  return supportsOnlyOfficePreview(document)
+}