feat(ERP-236): refine ConvertVideoController — entity filter, min-age window, proc_op...

feat(ERP-236): refine ConvertVideoController — entity filter, min-age window, proc_open fix

- Filter by entity=write_offs_products_erp_video (only write-off videos, not all files)
- Add --min-age=2h param: skip files younger than 2h (queue still processing)
- Reduce default --days from 10 to 2 (cron safety net for queue failures)
- Fix PHP hanging: switch from exec/system to proc_open with /dev/null pipes
- Fix timeout: raise from 600s to 1800s for large files
- Update actionStatus: show write-off video stats only (MOV+AVI / MP4)
- Update WriteOffsErp: change border date from -2 month to -1 month
- Add WriteOffsAttachmentsController: sync border_date comment
- Add erp24/docs/diagrams/convert-video-controller.html

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>