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>

server/cmd/worker-generate/main.go

@@ -65,6 +65,16 @@ func main() {
 		app.Config.LLM.MaxOutputTokens,
 	).WithCache(app.Cache)
 
+	imitationSvc := tenantapp.NewArticleImitationService(
+		app.DB,
+		app.LLM,
+		nil,
+		knowledgeSvc,
+		app.GenerationStreams,
+		generationCfg,
+		app.Config.LLM.MaxOutputTokens,
+	).WithCache(app.Cache)
+
 	kolWorker := generateworker.NewKolGenerationWorker(
 		app.DB,
 		app.LLM,
@@ -82,6 +92,7 @@ func main() {
 		app.RabbitMQ,
 		templateSvc,
 		promptRuleSvc,
+		imitationSvc,
 		kolWorker,
 		app.Logger,
 		app.Config.Generation,