feat(generation): migrate article generation and template-assist to RabbitMQ queues

Replace in-process generation with queue-based async execution via
RabbitMQ. Add generation task runtime for lifecycle management, article
generation payload/queue abstractions, and template-assist queue publisher.
Refactor prompt generation service to support batch generation with
per-item error tracking. Update stream hub to bridge queue events to SSE.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/internal/tenant/app/knowledge_service.go

@@ -219,7 +219,6 @@ func NewKnowledgeService(
 			go svc.runParseWorker()
 		}
 		go svc.recoverPendingParseTasks()
-		go svc.runDeletedCleanupWorker()
 	}
 
 	return svc
@@ -1753,17 +1752,6 @@ func (s *KnowledgeService) cleanupDeletedKnowledgeItemAsync(tenantID, itemID int
 	}()
 }
 
-func (s *KnowledgeService) runDeletedCleanupWorker() {
-	s.scheduleDeletedKnowledgeCleanup()
-
-	ticker := time.NewTicker(defaultKnowledgeCleanupPoll)
-	defer ticker.Stop()
-
-	for range ticker.C {
-		s.scheduleDeletedKnowledgeCleanup()
-	}
-}
-
 func (s *KnowledgeService) scheduleDeletedKnowledgeCleanup() {
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
@@ -1778,6 +1766,13 @@ func (s *KnowledgeService) scheduleDeletedKnowledgeCleanup() {
 	}
 }
 
+func (s *KnowledgeService) RunDeletedCleanupSweep() {
+	if s == nil {
+		return
+	}
+	s.scheduleDeletedKnowledgeCleanup()
+}
+
 func (s *KnowledgeService) listKnowledgeCleanupCandidates(
 	ctx context.Context,
 	limit int,