feat(imitation): add article imitation create flow

Introduce 仿写创作: new list and create views, backend imitation service
and prompt templates, worker task routing for imitation jobs, and one-click
rewrite triggers from question citation sources. Surface source article
URL/title on article list/detail, and restrict failed articles to delete-only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/components/PublishArticleModal.vue

@@ -508,13 +508,6 @@ function normalizePlatformUid(value?: string | null): string {
         </div>
       </section>
 
-      <a-alert
-        type="info"
-        show-icon
-        message="发布调度规则"
-        description="客户端在线时会立即开始消费；客户端离线时也允许提交，任务会先写入 SaaS 队列，客户端恢复在线后继续执行。"
-      />
-
       <section class="publish-modal__section">
         <div class="publish-modal__section-header">
           <h3><span class="required-star">*</span> 目标账号</h3>