[FEATURE]: Repository Health & Contributor Analytics

### Feature and its Use Cases

## What does it do?
This feature analyzes GitHub organizations and repositories to generate a clear health overview for each project. It combines repository activity, issue health, contributor diversity, bus factor, and historical issue/PR trends into a unified analytical model.

The system classifies repositories as Thriving, Active, Dormant, or Hibernating based on recent activity. It also calculates a health score, identifies contributor concentration risk, detects cross-organization contributors, and supports CSV exports for reporting.

## Benefits
Users can quickly understand which repositories are healthy, which ones need attention, and where maintenance risks exist. Instead of manually checking stars, issues, contributors, and activity across many repositories, this feature summarizes everything into useful signals.

It helps teams:
- Identify inactive or risky repositories.
- Find important contributors and cross-org connectors.
- Detect projects with low contributor diversity.
- Track issue and pull request activity over time.
- Export repository, contributor, and trend data for reports or audits.
- Prioritize maintenance work based on health and activity.

### Additional Context

_No response_

### Code of Conduct

- [x] I have joined the [Discord server](https://discord.gg/hjUhu33uAn) and will post updates there
- [x] I have searched existing issues to avoid duplicates

The issue names no files, tests, or entry points. Start by mapping the existing GitHub organization and repository data, analytics, dashboard, and CSV export areas, then clarify which health states, scores, contributor metrics, trends, and exports are in scope. Done means the agreed repository health and contributor analytics are available with the specified reporting outputs.

索引モデルが issue の本文から書いたものです。