feat(announcement): 新增首页弹窗公告功能并完成弹窗UI视觉重构

- 数据库与后端：announcements 表增加 is_popup 字段及迁移脚本，提供前台弹窗接口与多公告优先级选取，补全选优单测
- 管理后台：总后台与分销后台公告编辑新增「弹窗公告」开关与列表标签展示
- 前台交互：前台 PC/移动端首页引入 AnnouncementPopup，支持同一用户同一天同一公告仅弹一次的关闭记录
- 视觉优化：重构弹窗结构，顶栏镶嵌品牌橙流光细条与浅暖橙通知徽标，中间内嵌浅灰舒适阅读卡片，底部搭配大锤橙实心主操作按钮
- 验证方式：后端 announcement 单测通过，前端 npm run build 编译无报错，浏览器实机截图验证

frontend/src/features/admin/api/adminAnnouncements.ts

@@ -11,6 +11,8 @@ export interface CreateAnnouncementRequest {
   priority?: number
   is_pinned?: boolean
   is_important?: boolean
+  /** 弹窗公告：前台首页弹出且需用户手动关闭，同一天只弹一次 */
+  is_popup?: boolean
 }
 
 export interface UpdateAnnouncementRequest {
@@ -20,6 +22,7 @@ export interface UpdateAnnouncementRequest {
   priority?: number
   is_pinned?: boolean
   is_important?: boolean
+  is_popup?: boolean
 }
 
 export async function fetchAdminAnnouncements(params: {

frontend/src/features/admin/components/AnnouncementDialog.vue

@@ -55,6 +55,7 @@ const formData = ref<CreateAnnouncementRequest>({
   priority: 0,
   is_pinned: false,
   is_important: false,
+  is_popup: false,
 })
 
 // 站点列表：0=主站（默认），其余为分站；公告归属站点只在新建时可选。
@@ -118,6 +119,7 @@ watch(
           priority: props.announcement.priority,
           is_pinned: props.announcement.is_pinned,
           is_important: props.announcement.is_important,
+          is_popup: props.announcement.is_popup,
         }
       } else {
         formData.value = {
@@ -128,6 +130,7 @@ watch(
           priority: 0,
           is_pinned: false,
           is_important: false,
+          is_popup: false,
         }
       }
       void loadDistributionSites()
@@ -390,6 +393,13 @@ function escapeMarkdownImageText(text: string) {
       <el-form-item label="标记">
         <el-checkbox v-model="formData.is_pinned">置顶</el-checkbox>
         <el-checkbox v-model="formData.is_important" style="margin-left: 20px">重要</el-checkbox>
+        <el-checkbox v-model="formData.is_popup" style="margin-left: 20px">弹窗公告</el-checkbox>
+      </el-form-item>
+
+      <el-form-item v-if="formData.is_popup" label=" ">
+        <span class="popup-tip">
+          该公告会在对应站点首页弹出，用户必须手动点击「我知道了」才能关闭；同一天同一条只弹一次，次日重新弹出。多条弹窗公告同时启用时只弹优先级最高的一条。
+        </span>
       </el-form-item>
     </el-form>
 
@@ -502,6 +512,12 @@ function escapeMarkdownImageText(text: string) {
   flex-wrap: wrap;
 }
 
+.popup-tip {
+  color: #909399;
+  font-size: 13px;
+  line-height: 1.6;
+}
+
 :deep(.el-textarea__inner) {
   font-family: 'SF Mono', 'Menlo', 'Consolas', monospace;
   font-size: 13px;

frontend/src/features/admin/views/AdminAnnouncementsView.vue

@@ -308,6 +308,9 @@ function getStatusType(status: string): '' | 'success' | 'info' | 'warning' {
                 <el-tag v-if="row.is_important" type="danger" size="small" effect="plain"
                   >重要</el-tag
                 >
+                <el-tag v-if="row.is_popup" type="primary" size="small" effect="plain"
+                  >弹窗公告</el-tag
+                >
               </div>
             </div>
           </template>