Add fresh BpkCellItem documentation screenshots

Generated fresh screenshots for all BpkCellItem variants:
- Default
- With Chevron
- With Switch
- With Text
- With Link (with underline visible)
- With Image
- Surface Low Contrast
- Rounded Corner
- Surface Low Contrast + Rounded

Total: 18 screenshot files (9 variants × 2 modes: light + dark)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: YogiPatelSkyScanner