Remove deprecated generic CI/CD setup files

Remove unused generic setup-ci.md and setup-cd.md files that have been
replaced by platform-specific documentation in github/ and gitlab/ subdirectories.

Files removed:
- docs/7-cicd/setup-ci.md (replaced by github/setup-ci.md and gitlab/setup-ci.md)
- docs/7-cicd/setup-cd.md (replaced by github/setup-cd.md and gitlab/setup-cd.md)
- docs/assets/images/7-cicd/verify-setup-ci.png (replaced by platform-specific images)
- docs/assets/images/7-cicd/verify-setup-cd.png (replaced by platform-specific images)

These files were not referenced in mkdocs.yml navigation and contained
outdated GitHub Action-based workflows that have been superseded by
the new recce-cloud CLI approach.

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

Co-Authored-By: Claude <[email protected]>
Signed-off-by: even-wei <[email protected]>

Author: even-wei