fix: dos in annotation import (#29470)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/tasks/annotation/batch_import_annotations_task.py

@@ -30,6 +30,8 @@ def batch_import_annotations_task(job_id: str, content_list: list[dict], app_id:
     logger.info(click.style(f"Start batch import annotation: {job_id}", fg="green"))
     start_at = time.perf_counter()
     indexing_cache_key = f"app_annotation_batch_import_{str(job_id)}"
+    active_jobs_key = f"annotation_import_active:{tenant_id}"
+
     # get app info
     app = db.session.query(App).where(App.id == app_id, App.tenant_id == tenant_id, App.status == "normal").first()
 
@@ -91,4 +93,13 @@ def batch_import_annotations_task(job_id: str, content_list: list[dict], app_id:
             redis_client.setex(indexing_error_msg_key, 600, str(e))
             logger.exception("Build index for batch import annotations failed")
         finally:
+            # Clean up active job tracking to release concurrency slot
+            try:
+                redis_client.zrem(active_jobs_key, job_id)
+                logger.debug("Released concurrency slot for job: %s", job_id)
+            except Exception as cleanup_error:
+                # Log but don't fail if cleanup fails - the job will be auto-expired
+                logger.warning("Failed to clean up active job tracking for %s: %s", job_id, cleanup_error)
+
+            # Close database session
             db.session.close()