feat(desktop): 稳定桌面端界面与文件操作反馈

- 重构 DesktopPreferences 为分栏式设置面板，整合连接、外观、通知、更新与诊断信息分区，并补充过渡动效与暗色主题样式
- DesktopLayout 侧边栏导航分组支持展开折叠，调整管理/项目区块顺序并统一图标与标题
- 新增 fileTaskFeedback 工具，统一 pickFiles/saveFile/openFile 的成功/取消提示，替换审计导出、权限日志、附件、文档、线程、项目配置等处的直接调用
- desktopUpdateManager 暴露更新状态快照与状态变更监听，区分检查中、安装中、已推迟、失败等状态
- DesktopServerSettings 增加连接诊断信息（检查时间、健康地址、耗时、HTTP 状态）
- unified-page.css 与 ProjectMilestones 引入 CSS 变量以适配暗色主题
- WebLayout 将服务器设置入口改为打开系统偏好面板，管理菜单中邮件服务归入系统设置分组
- ProfileSettings 移除已迁入偏好面板的桌面端专属区块
- 补充 Layout.desktop 布局与偏好面板契约测试

frontend/src/views/documents/DocumentDetail.vue

@@ -378,8 +378,8 @@ import { useRoleTemplateMeta } from "../../composables/useRoleTemplateMeta";
 import { usePermission } from "../../utils/permission";
 import StateError from "../../components/StateError.vue";
 import StateLoading from "../../components/StateLoading.vue";
-import { openFile, pickFiles, saveFile } from "../../runtime";
 import { onDesktopRefreshCurrentView } from "../../composables/useDesktopRefresh";
+import { openFileWithFeedback, pickFilesWithFeedback, saveFileWithFeedback } from "../../utils/fileTaskFeedback";
 
 const route = useRoute();
 const auth = useAuthStore();
@@ -524,7 +524,7 @@ const uploadDirtyGuard = useDrawerDirtyGuard(() => ({
 }));
 
 const triggerFileInput = async () => {
-  const [file] = await pickFiles({
+  const [file] = await pickFilesWithFeedback({
     multiple: false,
     accept: ["pdf", "doc", "docx", "xls", "xlsx", "ppt", "pptx", "txt", "png", "jpg", "jpeg"],
     title: "选择文档版本",
@@ -813,7 +813,7 @@ const downloadVersion = async (version: DocumentVersion) => {
     const contentType = response.headers?.["content-type"] || "application/octet-stream";
     const filename = getFilename(response.headers?.["content-disposition"]) || `document-${version.version_no || version.id}.bin`;
     const blob = new Blob([response.data], { type: contentType });
-    await saveFile({ suggestedName: filename, mimeType: contentType, data: blob });
+    await saveFileWithFeedback({ suggestedName: filename, mimeType: contentType, data: blob });
   } catch (e: any) { ElMessage.error(e?.response?.data?.message || TEXT.common.messages.downloadFailed); }
 };
 
@@ -822,7 +822,7 @@ const openVersion = async (version: DocumentVersion) => {
     const response = await downloadDocumentVersion(version.id);
     const contentType = response.headers?.["content-type"] || "application/octet-stream";
     const filename = getFilename(response.headers?.["content-disposition"]) || `document-${version.version_no || version.id}.bin`;
-    await openFile({
+    await openFileWithFeedback({
       suggestedName: filename,
       mimeType: contentType,
       data: new Blob([response.data], { type: contentType }),