- Added cancel_job method to QueueManager for cancelling running jobs
- Added /job/<id>/cancel route in web.py for cancelling jobs via POST
- Updated history.html template to show:
  - Cancel button for processing jobs (orange button)
  - Delete button for cancelled jobs (red button)
  - Cancelled status styling (gray background)
- Added JavaScript updateJobActions function for dynamic action updates
- Modified worker_analysis.py to check for job cancellation during processing:
  - Added check_job_cancelled function to query database
  - Modified analyze_media to check cancellation before each frame and summary
  - Workers now stop processing and return 'Job cancelled by user' message
- Updated queue.py to pass job_id in data sent to workers for cancellation checking
- Job cancellation works for both local and distributed workers

Users can now cancel running analysis jobs from the history page, and cancelled jobs can be deleted from history.