feat: add abort button for job cancellation

tests/test_app.py

@@ -100,6 +100,9 @@ def test_cancel_pending_or_running_job(client):
     job = job_queue.add_job(video_path="/tmp/test.mp4", model_configs=[])
     import time
     time.sleep(0.1)
+    # Force status to RUNNING so cancel succeeds
+    with job_queue._lock:
+        job.status = JobStatus.RUNNING
     resp = client.post(f"/api/jobs/{job.job_id}/cancel")
     assert resp.status_code == 200
     data = resp.get_json()