perf(admin): 实现切页即时导航与列表 loading 壳

非阻塞 session 刷新、侧边栏 chunk 预取、KeepAlive 对齐，以及按 tab 延迟加载重型列表页。

apps/admin/src/composables/useStaleList.ts

@@ -0,0 +1,27 @@
+import { ref, onMounted, onActivated } from 'vue';
+
+/**
+ * 列表页 mount / KeepAlive activated 生命周期：有缓存则后台静默刷新，无缓存则显示 loading。
+ */
+export function useStaleListLifecycle(
+  hasData: () => boolean,
+  loadFn: () => void | Promise<void>,
+) {
+  const loading = ref(false);
+
+  async function runLoad(showSpinner: boolean) {
+    if (showSpinner) loading.value = true;
+    try {
+      await loadFn();
+    } finally {
+      loading.value = false;
+    }
+  }
+
+  onMounted(() => void runLoad(!hasData()));
+  onActivated(() => {
+    if (hasData()) void runLoad(false);
+  });
+
+  return { loading, runLoad };
+}