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/repository/audit_repo.go

@@ -70,9 +70,12 @@ func (r *auditRepository) CreateAuditLog(ctx context.Context, input AuditLogInpu
 }
 
 func (r *auditRepository) CreateGenerationTask(ctx context.Context, input GenerationTaskInput) (int64, error) {
-	operatorID := input.OperatorID
+	var operatorID *int64
+	if input.OperatorID > 0 {
+		operatorID = &input.OperatorID
+	}
 	return r.q.CreateGenerationTask(ctx, generated.CreateGenerationTaskParams{
-		OperatorID:         pgInt8(&operatorID),
+		OperatorID:         pgInt8(operatorID),
 		TenantID:           input.TenantID,
 		ArticleID:          pgInt8(input.ArticleID),
 		QuotaReservationID: pgInt8(input.QuotaReservationID),