后台统一状态提示：共享 toast 模块（ToastStack 挂后台布局与登录页），登录成功/失败、文章/标签/作品/文件/评论/设置操作全部有反馈，替换掉原生 alert；编辑器局部 toast 并入共享实现

frontend/src/admin/FilesView.vue

@@ -1,5 +1,6 @@
 <script setup>
 import { computed, onBeforeUnmount, onMounted, ref, watch } from 'vue'
+import { toastOk, toastErr } from './toast'
 import { useRoute, useRouter } from 'vue-router'
 import { adminApi } from '../api'
 import { relativeDate } from '../utils'
@@ -55,8 +56,10 @@ async function upload(files) {
     const fd = new FormData()
     for (const f of files) fd.append('file', f)
     await adminApi.uploadFiles(fd)
+    toastOk(`已上传 ${files.length} 个文件`)
     await load()
   } catch (e) {
+    toastErr(e.message || '上传失败')
     uploadError.value = e.message || '上传失败'
   } finally {
     uploading.value = false
@@ -75,6 +78,7 @@ function onDrop(e) {
 async function copyUrl(f) {
   try {
     await navigator.clipboard.writeText(f.url)
+    toastOk('链接已复制')
     copiedId.value = f.id
     setTimeout(() => {
       if (copiedId.value === f.id) copiedId.value = 0
@@ -89,10 +93,12 @@ async function remove(f) {
   if (!window.confirm(`删除「${f.name}」？存储里的文件会一并删除，引用它的文章将失效。`)) return
   try {
     await adminApi.deleteFile(f.id)
+    toastOk(`已删除「${f.name}」`)
     // 当前页删空时退一页，其余直接重载
     if (items.value.length === 1 && page.value > 1) router.replace({ query: { ...route.query, page: page.value - 1 } })
     else load()
   } catch (e) {
+    toastErr(e.message || '删除失败')
     error.value = e.message || '删除失败'
   }
 }