feat: 支持 ONLYOFFICE 持久化配置管理

- 添加 SettingsRenderForm schema 和 renderForm 字段
- 实现数据库 schema 自动迁移（onlyoffice_enabled, onlyoffice_public_url, onlyoffice_jwt_secret_encrypted）
- 新增 resolve_onlyoffice_settings() 函数支持运行时配置解析
- 知识库服务改用数据库配置替代运行时配置
- 前端添加文件渲染配置页面，支持 JWT 密钥管理
- 完善相关测试覆盖

web/src/views/scripts/PoliciesView.js

@@ -24,6 +24,7 @@ import {
   shouldRenderOnlyOfficePreview
 } from './knowledgePreviewMode.js'
 import { resolveKnowledgePreviewLayoutState } from './knowledgePreviewLayout.js'
+import { resolveInitialKnowledgeFolder } from './knowledgeFolderSelection.js'
 import { buildOnlyOfficePreviewConfig } from './onlyOfficePreviewConfig.js'
 
 function triggerFileDownload(blob, filename) {
@@ -80,7 +81,7 @@ export default {
     const { toast } = useToast()
 
     const documentSearch = ref('')
-    const activeFolder = ref('差旅规范')
+    const activeFolder = ref('')
     const folders = ref([])
     const documents = ref([])
     const selectedDocument = ref(null)
@@ -260,10 +261,7 @@ export default {
         documents.value = payload.documents || []
         emit('summary-change', { totalDocuments: documents.value.length })
 
-        const activeExists = folders.value.some((folder) => folder.name === activeFolder.value)
-        if (!activeExists) {
-          activeFolder.value = folders.value[0]?.name || ''
-        }
+        activeFolder.value = resolveInitialKnowledgeFolder(folders.value, activeFolder.value)
 
         if (options.preserveSelection && selectedDocument.value?.id) {
           const exists = documents.value.some((doc) => doc.id === selectedDocument.value.id)