[Remotion] Hero composition

## Summary
Create Remotion composition for hero section showing full UI overview.

## Scene
- Full PageSpace UI (sidebar, main panel, AI panel)
- Quick workflow demonstration
- Creating a page, AI editing, collaboration

## Duration
20-30 seconds

## Acceptance Criteria
- [ ] Full UI visible
- [ ] Key workflows shown
- [ ] Professional quality
- [ ] Exportable to MP4 for social