update seed scripts to prevent sql error when reloading install page

- tempfile uniqueness ensures that each process lives in its independent context
- add
writable/temp folder to store video clips temporary resources
- add videoClipWorkers config to
Admin for specifying the number of ffmpeg processes to run in parallel
- update video clip preview
background to better suit the end result

update job duration label for video clips list

go back to form after submitting an edit form

update Forms.Section component to adapt to full width

feat(video-clip): generate video clips in the bg using a cron job + add video clip page + tidy up UI