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/display.ts

@@ -77,6 +77,9 @@ export function getSourceTypeLabel(sourceType?: string | null, generationMode?:
   if (sourceType === "free_create") {
     return i18n.global.t("status.sourceType.free_create");
   }
+  if (sourceType === "imitation") {
+    return i18n.global.t("status.sourceType.imitation");
+  }
   if (sourceType === "kol") {
     return i18n.global.t("status.sourceType.kol");
   }