feat: Implement GitHub ProjectsV2 integration with project board status tracking

- Add project board status functionality using GitHub ProjectsV2 GraphQL API
- Create gh_issue_project_status table to store project board status data
- Implement GitHubService.getProjectBoardStatus() method with proper field extraction
- Add project-status.php page to display project board status dashboard
- Update status-board.php to use real project board status data
- Fix GraphQL schema issues for ProjectV2ItemFieldSingleSelectValue
- Add project board status import to getGHIssues workflow
- Clean up all test scripts and temporary files
- Update README.md with project board status documentation

This enables real-time tracking of issue status from GitHub ProjectsV2 boards,
replacing intelligent mapping with actual project board status data.

Author: Automation