assets: add portfolio images, staff photos, and background videos

- Add portfolio project screenshots (acs2, cdc, pifm, sf_heart, taxcoursecentral, etc.)
- Add staff photos (corbin, kevin, larrygoodrie, tom)
- Add background videos for portfolio, contact, and services pages
- Add video poster/cover images
- Optimize macbook-typing-poster.jpg

Author: actions-user