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/lib/article-list-actions.ts

@@ -19,7 +19,7 @@ export function resolveArticleActionState(generateStatus?: string | null): Artic
     };
   }
 
-  if (generateStatus === "draft" || generateStatus === "failed") {
+  if (generateStatus === "draft") {
     return {
       showPublish: false,
       showEdit: true,
@@ -29,6 +29,16 @@ export function resolveArticleActionState(generateStatus?: string | null): Artic
     };
   }
 
+  if (generateStatus === "failed") {
+    return {
+      showPublish: false,
+      showEdit: false,
+      showPreview: false,
+      showCopy: false,
+      showDelete: true,
+    };
+  }
+
   return {
     showPublish: false,
     showEdit: false,