feat: 前端页面优化与入库任务重试/删除

- 概览与检索合并为单一概览页
- 类目/文档管理/入库整合为树形目录知识库页（Library），支持文档搜索
- 入库进度改为右侧 Drawer，支持任务详情、重试、删除
- 后端新增任务重试与删除接口

frontend/src/layouts/MainLayout.vue

@@ -5,9 +5,6 @@ import { storeToRefs } from 'pinia'
 import { Modal, message } from 'ant-design-vue'
 import {
   DashboardOutlined,
-  FileTextOutlined,
-  UploadOutlined,
-  SearchOutlined,
   AppstoreOutlined,
   SettingOutlined,
   MenuFoldOutlined,
@@ -21,11 +18,14 @@ import {
 import { useAuthStore } from '@/stores/useAuthStore'
 import { changeMyPassword } from '@/api/auth'
 import { callApi } from '@/api/client'
+import TasksDrawer from '@/views/TasksDrawer.vue'
+import { useTasksDrawer } from '@/composables/useTasksDrawer'
 
 const route = useRoute()
 const router = useRouter()
 const authStore = useAuthStore()
 const { user, displayName } = storeToRefs(authStore)
+const tasksDrawer = useTasksDrawer()
 
 const collapsed = ref(false)
 
@@ -37,12 +37,9 @@ const openKeys = ref(['main'])
 
 const menuItems = computed(() => {
   const items = [
-    { key: 'overview', icon: () => h(DashboardOutlined), label: '概览' },
-    { key: 'documents', icon: () => h(FileTextOutlined), label: '文档管理' },
-    { key: 'ingest', icon: () => h(UploadOutlined), label: '文档入库' },
+    { key: 'overview', icon: () => h(DashboardOutlined), label: '概览与检索' },
+    { key: 'library', icon: () => h(AppstoreOutlined), label: '知识库' },
     { key: 'tasks', icon: () => h(ClockCircleOutlined), label: '入库进度' },
-    { key: 'search', icon: () => h(SearchOutlined), label: '检索测试台' },
-    { key: 'categories', icon: () => h(AppstoreOutlined), label: '类目列表' },
     { key: 'settings', icon: () => h(SettingOutlined), label: '设置' },
     { key: 'api-docs', icon: () => h(ApiOutlined), label: 'API 说明' }
   ]
@@ -53,6 +50,10 @@ const menuItems = computed(() => {
 })
 
 function handleMenuClick({ key }) {
+  if (key === 'tasks') {
+    tasksDrawer.open()
+    return
+  }
   if (key && key !== route.name) {
     router.push({ name: key })
   }
@@ -194,6 +195,9 @@ async function handleSubmitPassword() {
       </a-layout-footer>
     </a-layout>
 
+    <!-- 入库进度右侧 Drawer -->
+    <TasksDrawer />
+
     <!-- 强制改密弹窗（must_change_password 用户，不可关闭） -->
     <a-modal
       v-model:open="passwordModalVisible"