feat: SaaS (Multi-tenant GitHub App flow + org-scoped user stats)

[tim48-robot]

Summary

• Implement GitHub App install/setup flow and store per-server installation config
• Update pipeline to collect data per org and write org-scoped user stats
• Fix /getstats to read org-scoped stats for the current server
• Add /configure roles for custom role thresholds per server
• Update README with GitHub App envs, GH_APP secrets, and setup guidance

Why

Multi-organization support is now possible, and users can use the SaaS flow without manual tokens.

How to test

1. Invite bot to two Discord servers.
2. Run /setup in each and install the GitHub App to different orgs.
3. Run /link for a user in both servers.
4. Verify /getstats shows org-specific stats per server.

Notes

• GitHub Secrets required: GH_APP_ID, GH_APP_PRIVATE_KEY_B64
• Cloud Run envs required: GITHUB_APP_ID, GITHUB_APP_PRIVATE_KEY_B64, GITHUB_APP_SLUG

2025-12-27.02-19-40.mp4