fix: 软刷新齐套前保留旧画面，避免一点击就卸光

Logo/下拉静默预热后一次覆盖；commit 不再先 reset/loading；顺带会话预取与可配置 Feed 排序标签。

frontend/src/utils/softRefresh.ts

@@ -0,0 +1,20 @@
+import { prefetchLayoutShell, prefetchRoute } from './prefetchRoute';
+
+/** 软刷新齐套后的单一提交：各组件同一拍从 cache/快照同步 UI，禁止分批闪烁 */
+export const PAGE_SOFT_REFRESH_COMMIT_EVENT = 'page-soft-refresh-commit';
+
+/**
+ * 静默刷新当前页：不改画面、无进度条，预热齐套后派发一次 commit。
+ */
+export async function softRefreshCurrentPage(to?: string): Promise<void> {
+  const path = to ?? `${window.location.pathname}${window.location.search}`;
+  try {
+    await Promise.all([
+      prefetchRoute(path, { force: true }),
+      prefetchLayoutShell({ force: true }),
+    ]);
+  } catch {
+    // 仍派发 commit，让界面有机会用已有缓存自愈
+  }
+  window.dispatchEvent(new Event(PAGE_SOFT_REFRESH_COMMIT_EVENT));
+}