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/views/MediaLibrary.vue

@@ -1,5 +1,7 @@
 <script setup lang="ts">
-import { ref, computed, onMounted, watch } from 'vue';
+defineOptions({ name: 'AdminMediaLibrary' });
+
+import { ref, computed, onMounted, onActivated, watch } from 'vue';
 import { ElMessage, ElMessageBox } from 'element-plus';
 import { useAdminLocale } from '../composables/useAdminLocale';
 import api from '../api';
@@ -54,8 +56,8 @@ function formatDate(iso: string) {
   return new Date(iso).toLocaleString();
 }
 
-async function loadFiles() {
-  loading.value = true;
+async function loadFiles(opts?: { silent?: boolean }) {
+  if (!opts?.silent) loading.value = true;
   try {
     const params: Record<string, string | number> = { page: currentPage.value, pageSize };
     if (activeCategory.value) params.category = activeCategory.value;
@@ -65,7 +67,7 @@ async function loadFiles() {
   } catch {
     ElMessage.error(t('common.loading'));
   } finally {
-    loading.value = false;
+    if (!opts?.silent) loading.value = false;
   }
 }
 
@@ -74,9 +76,14 @@ watch(activeCategory, () => {
   loadFiles();
 });
 
-watch(currentPage, loadFiles);
+watch(currentPage, () => {
+  void loadFiles();
+});
 
-onMounted(loadFiles);
+onMounted(() => void loadFiles());
+onActivated(() => {
+  if (files.value.length > 0) void loadFiles({ silent: true });
+});
 
 async function confirmDelete(file: MediaFile) {
   await ElMessageBox.confirm(t('media.delete_confirm'), { type: 'warning' });